Optimal skin prick wheal size for diagnosis of cat allergy.

BACKGROUND: The skin prick test is the diagnostic procedure of choice for determination of immediate hypersensitivity. A wheal diameter of 3 mm or larger is generally accepted as the cutoff for a positive test result, although the validity of this assumption has not been rigorously demonstrated. OBJECTIVE: To determine the skin prick wheal size that best identifies clinical allergy to cat. METHODS: Forty-five patients referred for evaluation of rhinoconjunctivitis underwent determination of atopic status by skin testing using the Greer Dermapik device and a combination of other modalities, including history, in vitro determination of specific IgE level, and nasal challenge with standardized cat pelt extract. Parameters evaluated before and after nasal challenge included symptom score and nasal lavage tryptase and prostaglandin D (PGD2) levels. RESULTS: The widely accepted 3-mm wheal for a positive skin test result to cat is highly sensitive but only moderately specific for diagnosis of cat allergy as evaluated by history, specific IgE level, postchallenge symptom score, and tryptase and PGD2 levels. Optimal cutoffs for a positive skin test result to cat based on receiver operating characteristic analysis and 95% positive predictive value were 5.5 mm or greater for each of these parameters. When a true-positive result for cat allergy was defined as a combination of positive history, specific IgE level, postchallenge symptom score, and tryptase and PGD2 levels and a true-negative result as all of these parameters being negative, a 6-mm cutoff was able to distinguish cat allergic from cat nonallergic individuals. CONCLUSION: In a potentially allergic population undergoing skin prick testing with the Greer Dermapik using standardized extracts, a 3-mm skin prick wheal will overestimate the presence of cat allergy. A 6-mm wheal appears to distinguish those individuals who are cat allergic from those who are not.     

Cetirizine inhibits bradykinin-induced cutaneous wheal and flare in atopic and healthy subjects

BACKGROUND: Kinins are vasoactive mediators involved in allergic reactions. When applied on the skin or in the nose, bradykinin (BK) elicits inflammation that is poorly affected by previous H1-blockade. The aim of this study was to compare the possible effect of cetirizine (an H1-antagonist) on wheal and flare responses to BK, histamine, and compound 48/80 in atopic and healthy subjects. METHODS: In a randomized, double-blind, crossover study, eight atopic and eight healthy subjects received cetirizine (10 mg/day) or placebo for 3 days before cutaneous tests. Intradermal tests (IDT) and prick tests (PT) were performed with BK (20 nmol/ml for IDT and 20 micromol/ml for PT), histamine (100 microg/ml IDT and 100 mg/ml PT), and compound 48/80 (100 microg/ml IDT and 100 mg/ml PT) as positive controls and saline as negative control. The skin responses were monitored by measurement of wheal and flare areas. RESULTS: BK, histamine, and 48/80 induced wheal and flare reactions in all placebo-treated subjects. Histamine elicited larger wheal and flare reactions than BK and 48/80. IDT with BK induced four- to sixfold larger wheal and flare reaction than PT. No differences in BK-induced wheal and flare were observed between atopic and healthy subjects. In atopic subjects, cetirizine induced a significant reduction of flare reactions after the BK test (80% for IDT, and 94% for PT [P < 0.01]). Moreover, cetirizine reduced significantly BK-induced wheals by 70% for IDT (P < 0.01) and 65% for PT (P < 0.01). A similar inhibiting effect of cetirizine was also observed in healthy subjects. CONCLUSIONS: These findings showed that the wheal and flare reactions induced by BK challenge were markedly inhibited by previous intake of cetirizine. The mechanism by which this effect is mediated cannot be established at present.     

Cetirizine inhibits bradykinin-induced cutaneous wheal and flare in atopic and healthy subjects

BACKGROUND: Kinins are vasoactive mediators involved in allergic reactions. When applied on the skin or in the nose, bradykinin (BK) elicits inflammation that is poorly affected by previous H1-blockade. The aim of this study was to compare the possible effect of cetirizine (an H1-antagonist) on wheal and flare responses to BK, histamine, and compound 48/80 in atopic and healthy subjects. METHODS: In a randomized, double-blind, crossover study, eight atopic and eight healthy subjects received cetirizine (10 mg/day) or placebo for 3 days before cutaneous tests. Intradermal tests (IDT) and prick tests (PT) were performed with BK (20 nmol/ml for IDT and 20 micromol/ml for PT), histamine (100 microg/ml IDT and 100 mg/ml PT), and compound 48/80 (100 microg/ml IDT and 100 mg/ml PT) as positive controls and saline as negative control. The skin responses were monitored by measurement of wheal and flare areas. RESULTS: BK, histamine, and 48/80 induced wheal and flare reactions in all placebo-treated subjects. Histamine elicited larger wheal and flare reactions than BK and 48/80. IDT with BK induced four- to six-fold larger wheal and flare reaction than PT. No differences in BK-induced wheal and flare were observed between atopic and healthy subjects. In atopic subjects, cetirizine induced a significant reduction of flare reactions after the BK test (80% for IDT, and 94% for PT [P<0.01]). Moreover, cetirizine reduced significantly BK-induced wheals by 70% for IDT (P<0.01) and 65% for PT (P<0.01). A similar inhibiting effect of cetirizine was also observed in healthy subjects. CONCLUSIONS: These findings showed that the wheal and flare reactions induced by BK challenge were markedly inhibited by previous intake of cetirizine. The mechanism by which this effect is mediated cannot be established at present.     

Leukotriene C4 and histamine in early allergic reaction in the nose

We have examined the measurements of LTC4 and histamine in nasal lavage fluids and blown secretions as a possible model of the early mediator events during nasal allergy. A nasal challenge with grass pollen extract was undertaken on two separate occasions in 20 patients with a history of seasonal rhinitis and a positive immediate skin test to grass pollen. A 2 ml nasal lavage was performed before allergen challenge, and blown secretion collected separately 15 min after the provocation, followed by a final 2 ml nasal lavage. The dilution of nasal secretion by the lavage fluid was determined using 99mTc-labelled albumin as an exogenous marker added to the fluid. The amounts of admixture in the nasal lavages did not correlate to the concentrations of LTC4 and histamine, indicating that the variable amounts of nasal secretion in nasal lavage do not constitute a confounding variable for measurements of LTC4 and histamine. In the pre-challenge lavages, the median concentrations, of LTC4 and histamine were 1.7 and 52 nmol/l respectively. Following allergen challenge neither LTC4 nor histamine measured in nasal lavage showed any significant change from pre-challenge baseline values. However, measurements of both mediators in the blown secretion showed a significantly higher concentration than in the pre- or post-challenge lavage samples, compatible with transitory release during the acute allergic reaction. However, it seems doubtful whether measurements of LTC4 or histamine can be compared between blown secretion and nasal lavage fluid, even if the dilution factor is disregarded.(ABSTRACT TRUNCATED AT 250 WORDS)     

Relationship between the results of bronchial, nasal and conjunctival provocation tests in patients with asthma

Skin tests and bronchial, nasal and conjunctival provocation tests with pollen and animal dander allergens were performed in thirty patients with atopic asthma. In vivo test results were compared only when the same batch of allergen had been used. A nasal reaction was mostly elicited at a lower concentration of allergen than was needed to elicit a bronchial reaction (P < 0·01). Positive nasal reactions were often obtained when the corresponding bronchial tests were negative. The conjunctiva reacted to lower concentrations than the bronchi in a third of the instances of testing, with most of these being tests with mugwort allergen (P < 0·05). A positive skin test in cases with a negative bronchial challenge test was often accompanied by a positive nasal test and in some cases by a positive conjunctival test. It is concluded that nasal or conjunctival provocation tests do not replace bronchial challenge tests. In an asthmatic patient who gives no reaction to bronchial challenge with a particular allergen, a positive skin test may reflect a nasal allergy.     

Duration of the antihistaminic effect after discontinuationof ebastine

BACKGROUND: The inhibitory effect of antihistamines on allergen-induced skin reactions can impair the results of allergen skin testing, which are necessary for the diagnosis of atopic diseases. This study was designed to determine the time period required for the inhibitory effect of ebastine on allergen-induced skin reactivity to disappear completely. METHODS: This was a double-blind, placebo-controlled, parallel-group study including 23 out of 27 randomized patients. They received either ebastine 20 mg or placebo once daily for 7 days. At the end of treatment, allergen challenge was performed daily for 7 days. Histamine challenge was performed on day 1 (6 and 24 h) and day 5 after treatment. The wheal and flare surface areas were measured and analyzed. RESULTS: Highly significant inhibition of the wheal and flare response induced by allergen was observed after ebastine treatment on days 1 and 2 as compared with placebo (P < 0.01 for both). The inhibition was reduced, although still significant, by day 3 (P < 0.05). No significant difference was observed by day 4 between the ebastine and the placebo groups. The effects of histamine challenge were significantly reduced in the ebastine compared with the placebo group at day 1 (6 and 24 h), and were similar at day 5 after treatment. CONCLUSION: Our results show that the wheal and flare response to allergen after ebastine discontinuation returns to placebo values after 4 days. Therefore, patients using ebastine need to be antihistamine-free for 4 days before the skin prick test. This is valuable information for the allergologist seeking to diagnose allergen sensitivity.     

Skin Prick Testing and the Use of Histamine References

The skin prick test is a fundamental test in biological allergen standardization and in evaluation of changes in skin sensitivity due to treatment. The allergen concentration eliciting a wheal equal to that produced by histamine 1 mg/ml is generally accepted as the skin sensitivity. Using a standardized quantitative skin prick test, 25 mould allergic patients were tested with quadruplicate determinations of five 10-fold allergen concentrations of highly purified and standardized extracts. Histamine 1 and 10 mg/ml were used as positive references. The 10-fold increase of histamine resulted in a doubling of the histamine reaction and increased the mean wheal diameter from 4 to 7 mm. The correlation between skin sensitivity estimated by histamine 1 and 10 mg/ml is significant, but with a dissociation between the two ways of estimating the sensitivity of 0.25 log step in the low sensitivity range and 1.8 log step in the high sensitivity range (the difference at median sensitivity is 1 log step). No correlation was found between histamine- and allergen-induced wheal area increase, and the discrepancy might be caused by a difference in the endogenous histamine release and/or difference in the number of histamine receptors at different degrees of sensitivity. With the use of median values it is possible to perform biological standardization with histamine 10 mg/ml and interpolate to histamine 1 mg/ml. However, the response in individual patients varies, and because of the small wheal area and the low reproducibility with histamine 1 mg/ml we recommend the exchange of histamine 1 mg/ml to histamine 10 mg/ml as an international positive reference.     

Type I allergy to egg and milk proteins: comparison of skin prick tests with nasal, buccal and gastric provocation tests

Provocation tests with egg or milk antigens were performed on symptomatic patients or those who were skin prick test positive to these antigens. Skin test positive patients responded immediately in 12/13 to nasal, in 7/15 to buccal and in 5/15 to gastric provocation tests. An immediate gastric response was within 1 h. The threshold dose for a positive result showed that tissue sensitivity from greatest to least was in the order: skin, nasal, buccal and gastric. None of the skin test negative group responded to any of the provocation tests. The results, particularly the nasal provocation, validate the skin prick test as a sensitive measure of type I allergy to defined foods. The relative insensitivity of buccal and gastric mucosae may explain positive skin test responses in asymptomatic subjects.     

Australian pine (Casuarina equisetifolia) pollen as an aeroallergen

Sixty-seven nasal and bronchial provocation tests were performed with Australian pine pollen extract (APE) on 61 subjects. A positive nasal response was elicited in 10 of 14 (71%) subjects with allergic rhinitis and positive APE skin tests and in none of 23 control subjects with negative APE skin tests. A positive bronchial challenge was elicited in 5 of 10 (50%) extrinsic asthmatics with positive APE skin tests and in none of 20 control subjects with negative APE skin tests. Australian pine pollen-specific IgE was demonstrated by conventional RAST (greater than or equal to + 1) in 6 of 14 (42%) subjects with a positive nasal challenge, and in 4 of 5 (80%) subjects with a positive bronchial challenge. The Australian pine pollen is an aeroallergen.     

Reliability of skin prick tests during terfenadine treatment in adults with pollen rhinitis

The variation in skin prick test (SPT) results was evaluated clinically during terfenadine treatment in 39 adult patients with pollen rhinitis. A change in the perceived state of the patient as regards sensitization to a specific pollen allergen or atopic constitution was judged to be clinically important. A randomized, double-blind, crossover design was used, comprising 2 weeks on terfenadine 120 mg once a day and 2 weeks on placebo. SPT for two pollen allergens and histamine (10mg/ml) were evaluated at the start of the study and at the end of each period. When SPT was used as a discovery test and liberal definitions were applied, predictive values for a positive test were 100%. 1-Sensitivity ranged between 10 and 54% with substantially lower values when a histamine wheal reaction was noted. The inhibitory effect of terfenadine was detectable 2 weeks after withdrawal as a reduction in the median of the mean diameter for the histamine-induced wheal response of 1 mm (0–1.5). The data implied that a positive SPT is reliable when liberal definitions are adopted for sensitization and atopy; a negative SPT is presumably reliable when the measurement artifact is considered and the wheal reaction to histamine is detectable.     

Humoral and Cell-Mediated Immune Responses to Dog Dander and Hair in Asthmatic Children

Dog dander and hair (DDH) specific IgA, IgG and IgE antibodies from serum samples Of 202 asthmatic children, and in nasal secretion from 4 to 15 years were measured by enzyme-linked immunosorbent assay. The results were compared with clinical history, and with allergy test (skin prick test, provocation test and RAST) using the same DDH extract. A blood sample for the in vitro lymphocyte stimulation test was obtained from 40 children, and a nasal secretion sample for analysis of the local DDH-specific IgA, IgG and IgE antibody levels was collected form 35 of them. In children of dog-keeping families, higher serum levels of DDH-specific antibodies, especially IgE antibodies, were observed if the dog had been in the home already during the first years of the child's life. The serum levels of DDH-specific antibodies, however, did not correlate with the degree of the present exposure to dogs. The serum levels of DDH-specific or total IgE, or with the results of skin prick or provocation test. The serum levels of DDH-specific IgA were highest in children who were subjectively most sensitive to dogs. Nasal levels of DDH-specific IgE correlated positively with serum specific IgE levels. The correlation was weaker between nasal and serum titers of specific IgG, and not significant between nasal and serum IgA antibody levels, Specific IgE antibody levels were higher, while specific IgA and IgG antibody levels were lower, in nasal secretion form subjects with nasal symptoms on contact with dogs, when compared with subjects with other complaints (asthma, conjunctival or skin reactions). DDH-specific IgG levels correlated negatively with specific IgE level in the nasal secretion from subjects with a positive provocation test result, while the correlation was positive in subjects with a negative provocation test. The in vitro lymphocyte response to DDH did not correlate with the results of allergy test, or with the levels of DDH-specific antibodies in serum or in nasal secretion.     

The changes in the nasal secretions of eosinophils during the immediate nasal response to allergen challenge

In 162 patients with allergic rhinitis due to immediate hypersensitivity, nasal provocation tests (NPT) were supplemented by recording of the eosinophils in the nasal secretions (NS). Nasal secretion specimens were obtained before and repeatedly after allergen challenge and stained by a modified Hansel's method. The 188 positive immediate nasal responses (INR) that correlated with positive skin tests and history and 92 negative INR that correlated with negative skin tests and history were studied. Several different types of eosinophil response to allergen challenge were observed. Eosinophilia was found in the NS in 84% of patients with positive INR but in only 49% of patients with negative INR. The eosinophil count before allergen challenge was low in 79.5% of positive INR and in 76.5% of negative INR, whereas it was high in 20.5% of positive INR and in 23.5% of negative INR. The positive INR were accompanied by significant changes (p less than 0.01) in the eosinophil count between before and after allergen challenge in 74% and the negative INR in only 19% of the cases. These changes appeared within 30 min after allergen challenge. This study shows that only a single count of eosinophils in the NS is not a suitable indicator of nasal allergy. The recording of eosinophils in the NS can be considered as a useful supplementary diagnostic parameter for the possible involvement of immediate hypersensitivity in the nasal mucosa if (1) the eosinophil count is related to a certain allergen and (2) the eosinophils are recorded before and repeatedly up to 60 min after allergen challenge.     

Use of cetirizine to investigate non-H1 effects of second-generation antihistamines.

In addition to their increased potency as H1 blockers and their nonsedating effects, the second-generation antihistamines have other unusual and potentially beneficial properties. Evidence is accumulating from several laboratories that at least one of these agents under investigation, cetirizine, may be effective in inhibiting the late reaction. The Johns Hopkins group showed that during the cutaneous late phase response (LPR), histamine release was not altered by cetirizine, 20 mg, pretreatment. The most dramatic effect of cetirizine was attenuation of inflammatory cell migration into the chamber. Eosinophils, neutrophils, and basophils were reduced by about 75% during hours 6 to 8. It can be concluded that cetirizine influences the LPR by causing a reduction in the inflammatory cell infiltrate. Cetirizine, 10 mg, orally once a day also induced a significant decrease in the wheal and flare skin reactions caused by pollen, histamine, and compound 48/80. Cetirizine inhibited eosinophil recruitment and platelet-activating factor (PAF) in skin chambers 24 hours after pollen challenge. We and others have studied the mechanisms of this effect. The release of eosinophil peroxidase induced by PAF and formyl-methionyleucyl/phenylalanine was not attenuated by cetirizine. At therapeutic concentrations, however, cetirizine has a potent inhibitory action in vitro on eosinophil chemotaxis induced either by formyl-methionyleucyl/phenylalanine or PAF and also on IgE-dependent stimulation of platelets. In a separate study in patients with chronic urticaria, cetirizine markedly reduced both the immediate wheal and flare induced by PAF and the delayed reaction at six hours. These results suggest that cetirizine acts on eosinophil migration to inhibit the late reaction.     

Nasal provocation test in the diagnosis of natural rubber latex allergy

BACKGROUND: Natural rubber latex (NRL) allergy in workers using rubber gloves has been an occupational health problem for the last 10 years. In the case of the occupational agents, clinical history may be far from conclusive; hence, appropriate provocation should be carried out. The objective was to evaluate the usefulness of the nasal challenge test in the diagnosis of allergic rhinitis in subjects occupationally exposed to NRL. METHODS: A single-blind, placebo-controlled study was conducted in 16 nurses with respiratory symptoms (bronchial asthma and/or rhinitis) related to NRL exposure as well as positive skin prick test (SPT) response to NRL. The controls were nine nurses with asthma and/or perennial rhinitis unrelated to NRL exposure; six atopic patients not occupationally exposed to NRL, with asthma and/or perennial rhinitis; and six healthy subjects. All the controls had negative results of SPT with NRL. Patients with a history of anaphylaxis or positive results of RAST to NRL were not considered in the study. The "nasal pool" technique was used to evaluate the cellular response and changes in protein level and ECP concentration in nasal washings after topical provocation with allergen or placebo. RESULTS: A significant increase was noted in eosinophil and basophil number, albumin/total protein ratio, and ECP level only in NRL SPT-positive patients subjected to nasal challenge with NRL. Neither bronchial nor systemic reactions were found after the nasal provocation with NRL. CONCLUSIONS: The nasal challenge test appears to be useful for diagnosing occupational rhinitis in NRL-sensitized patients.     

Evaluation of the nasal provocation test for its necessity in the diagnosis of nasal allergy to house dust mite

The aim of this study was to evaluate rhinomanometric responses to nasal allergen provocation in children with allergic rhinitis sensitized to house dust mite. We studied 51 children, aged 6-16 years (mean: 11.5 +/- 2.6 years), with clinical symptoms of perennial allergic rhinitis without asthma and 20 non-atopic healthy controls in the same age range (mean: 11.8 +/- 3.8 years). All of the patients had positive skin prick test (SPT) results and serum specific IgE above 0.70 kU/l to Dermatophagoides pteronyssinus (Dp). Nasal provocation testing (NPT) was performed with increasing concentrations of Dp extracts and the nasal response was evaluated by active anterior rhinomanometry. A 100% increase of resistance in one or both nasal cavities was considered positive. There was a statistically significant difference of baseline nasal resistance (total, right and left sides) between the control and the patient groups (p < 0.001). A positive response to house dust mite allergens was recorded in 47/51 (92.2%) patients by rhinomanometry. The NPT presented no significant correlation with age, weight, height, SPT diameter, serum total and specific IgE levels to Dp and baseline nasal airway resistance values. This study suggests that a nasal provocation test with allergen is unnecessary in children with positive skin prick test and serum IgE specific to house dust mite. The rhinomanometric response to the allergen provocation does not correlate with the diameter of the skin prick test and the level of serum specific IgE.     

Silk-induced asthma in children: a report of 64 cases

A total of 64 children less than 15 years of age with asthma caused by silk were studied. The diagnosis was based on a history of wheezing, positive skin tests to silk, positive conjunctival or nasal provocation tests, or serum IgE-Sw (silk waste). The average age of onset was 4 years 2 months. Sex ratio (M:F) was 3.6:1. A positive skin test is essential for the diagnosis. Conjunctival provocation tests were performed in 80% of cases because of reliability, safety, and convenience. The first symptom appeared an average of 10 months after initial exposure to silk. In 61% of patients, asthma was accompanied by allergic rhinitis but in only 14% of cases by conjunctivitis. In most cases, asthma occurred in winter, due to seasonal use of bed quilts or clothes filled with silk. Silk is a highly potent allergen. The average mean wheal diameter elicited by silk in prick testing was larger than two histamine equivalent prick tests. A cross reactivity exists among mulberry silk, and silkworm cocoons, batryticated silkworms, and silkworm chrysalis.     

Improved diagnosis and treatment of allergic rhinitis by the use of nasal provocation tests

A simple and safe method of nasal provocation for out-patients that requires no special equipment is described. A total of 2,645 cases were tested by nasal provocation tests. Of the total, 1,175 were tested with Dermatophagoides pteronyssinus, 825 with mixed grass pollens, 352 with plantain (Plantago lanceolata), and 125 for cats and correlating nasal tests with skin tests yielded 80%, 90%, and 85%, respectively. Immunotherapy for allergic rhinitis was only considered justifiable when the nasal provocation test was positive. The nasal provocation test was repeated at the end of the normal course of injections recommended by the manufacturer. If the nasal provocation test was still positive, further injections were given until the test became negative. This method of improving diagnostic accuracy and monitoring results of immunotherapy was used with both aqueous extracts which were used for skin testing (Australian Government Commonwealth Serum Laboratories) and with Allpyral pyridine-extracted alum-precipitated extracts (Dome Laboratories, England). The number of injections of allergen required to convert a positive nasal provocation test to negative varied from 26 to 69 for mite aqueous injections with only 12 to 19 for mite suspension and 47 to 98 for grass aqueous injections compared with 12 to 36 for grass suspension. Direct provocation tests of the nose should give a more accurate diagnosis than RAST or skin tests and are required for monitoring therapy because considerable individual variations in sensitivity and response to treatment were demonstrated. Standard dosage schedules are not suitable for individual patients, who should have their immunotherapy personalized.     

Relationship between allergen-specific skin testing and nasal provocation in patients with perennial rhinitis.

Patients with perennial rhinitis were evaluated by allergen challenge epicutaneously and intranasally. Nasal provocation was assessed by clinical score, graded 0-12, to include rhinomanometry, secretions (mL), sneezes, and stuffy nose. All 40 patients with perennial symptoms had no clinical history of seasonal exacerbations but did have both positive skin tests and nasal provocation to the same allergen. Skin test wheel size correlation with nasal provocation (P less than .02).     

Time-dependent observations of secretion marker levels in nasal secretion after histamine and methacholine provocations

Nasal provocation tests with histamine and methacholine were carried out on 25 healthy men in an effort to assess the dynamic changes of albumin, total IgA, secretory IgA and lactoferrin concentrations in the nasal secretion. The trials were performed with 0.5, 1, and 4 mg of histamine and 8, 16, and 32 mg of methacholine. Each dose of histamine or methacholine was sprayed into the nose every 2nd day, with two days' interval between the two provoking agents. Nasal secretions were collected after saline spraying only, forming the baseline group, after 3, 10 and 15 min of administration of the challenge agent. The baseline levels presented the following values: for albumin 257 +/- 230 microg/ml, secretory IgA 608 +/- 379 microg/ml, total IgA 1025 +/- 423 micog/ml, and lactoferrin 213 +/- 156 microg/ml. The increase in albumin level after nasal provocation, particularly significant after histamine administration (to 3713 +/- 2311 microg/ml), indicates incessant protein plasma leakage from the blood circulation to the nasal secretion. After administration of both provocating agents, there was a significant gradual decrease in secretory IgA level, even below the baseline value. After the 2nd and 3rd doses of methacholine and histamine spray, the concentration of secretory IgA decreased by 2-3 times and was found to be 200-300 microg/ml, respectively. Also, lactoferrin concentration values decreased gradually after the 2nd and 3rd doses of methacholine and histamine to levels close the baseline value. These observations suggest a time- and dose-dependent, non-specific dysfunction of local immunity response after nasal provocations.     

Wheal-and-flare reactions induced by allergen and histamine: evaluation of blood flow with laser Doppler flowmetry

Dermal blood flow was evaluated after skin prick test with histamine and allergen in six patients with seasonal allergic rhinitis. Blood flow was registered continuously for 60 minutes after the test procedure with laser doppler flowmetry, which allows noninvasive measurements. Blood flow was measured close to the skin test in the wheal obtained, and at a greater distance from the prick in the flare reaction. Tests were performed with preloaded skin test needles with histamine and the appropriate allergen freeze-dried on the point of the lancet, as well as with the appropriate negative control. The prick test procedure, by itself, induced a transient increase in blood flow that was normalized again after 9 minutes for the closest measurement. Histamine induced a rapid increase in blood flow in both the flare and wheal reaction that was normalized after about 45 minutes. The increase was significantly higher in the flare compared to the wheal for the time points from 6 1/2 to 13 minutes. Allergen induced a similar increase in blood flow. However, the increase was not noticeable until 2 1/2 minutes after the allergen application and was not completely abolished within 60 minutes. Furthermore, the difference between the flare and wheal reaction, with the higher values for the flare reaction, was present for a longer period of time than for the equivalent histamine measurements. In conclusion, laser doppler flowmetry appears useful for continuous evaluation of vascular changes induced at skin prick tests.(ABSTRACT TRUNCATED AT 250 WORDS)