Allergic and toxic reactions in soft contact lens wearers

The allergic and toxic effects of preservatives found in soft contact lens solutions are reviewed. Thimerosal, a preservative commonly found in soft contact lens solutions, may cause ocular delayed hypersensitivity. Patients with delayed hypersensitivity to thimerosal may develop conjunctival hyperemia, corneal infiltrates and intolerance to lens wear with the use of soft contact lens solutions containing thimerosal. Delayed hypersensitivity to thimerosal can be demonstrated by an occlusive patch test or intradermal injection. Discontinuation of chemical disinfection with substitution of thermal disinfection using unit-dose, non-preserved saline causes resolution of signs and symptoms. Another cause of lens wear intolerance is contact lensassociated giant papillary conjunctivitis. Protein deposits on the lens may act as antigens and initiate an allergic condition which disappears when the lens is discontinued. Alternatively, the giant papillae may be the result of mechanical irritation induced by the contact lenses. The chemical preservatives that are found in soft contact lens solutions cause epithelial toxicity when applied to isolated rabbit corneas. However, corneal toxicity in a clinical setting has not been demonstrated.     

含蒽醌的中草药——一类潜在的天然抑菌防腐剂初探

[目的]探讨富含蒽醌类中草药作为天然防腐剂的可行性。[方法]将大黄、虎杖、决明子、何首乌、茜草分别提取检出蒽醌甙,进行抑菌试验及抑菌强度试验。[结果]虎杖和决明子对大肠杆菌,决明子和何首乌对产气杆菌,大黄和虎杖对金黄色葡萄球菌,大黄、虎杖和茜草对枯草杆菌,大黄和决明子对青霉分别有较强的抑制能力。虎杖、决明子对大肠杆菌的最低抑菌浓度为0.025和0.125g/mL;大黄、虎杖、决明子对金黄色葡萄球菌的最低抑菌浓度为0.003、0.003、0.125g/mL;大黄、决明子对青霉的最低抑菌浓度为0.031、0.063g/mL。[结论]蒽醌类中草药用做天然防腐剂前景看好。     

Complications of Preservatives in Contact Lens Solutions

ABSTRACT The addition of preservatives in contact lens solutions has been used as a means of killing bacteria or preventing their growth. With the widespread use of preservatives it has become increasingly evident that they have the ability of being adsorbed and absorbed by contact lenses. Consequently, the ocular tissues can be exposed to preservatives over a prolonged period of time. Since the 1970s practitioners have become aware of the adverse reactions resulting from the use of preservatives. The frequency of the complications attributed to the use of preservatives is difficult to ascertain, but most manufacturers and practitioners estimate it to be in the victinity of 5–10%. Preservatives have been shown to have a toxic effect on the cornea, causing disruption of cell structure and possible malfunction of epithelium, stroma and endothelium. In recent years preservatives, in particular thimerosal, have been recognized as having the ability to elicit allergic responses. This paper reviews the present literature on the complications of using preservatives. It concludes that much more research is needed in this area. Until the long term implications of preservatives in contact lens solutions are known, heat disinfection with non-preserved saline is a practical and safer alternative.     

Food Allergy Overview in Children

Food allergies have increased significantly in the past decade. An accurate history is crucial in approaching the management. At the outset, food intolerance must be distinguished from food allergies and, furthermore, these allergies should be classified into either an IgE, Non-IgE, or a mixed response. The clinical features vary from life-threatening anaphylaxis to milder IgE-mediated responses, atopic dermatitis, and gastrointestinal symptoms. The severity of the reaction and the potential risk for anaphylaxis on reexposure should be assessed. Milk, soy, egg, wheat, and peanut allergies are common in children, whereas peanut, tree nut, fish, shell fish allergies, and allergies to fruits and vegetables are common in adults. Structural proteins are important determinants of the severity of the reactions and may often predict the natural history and cross reactivity. Diagnostic work up must be guided by the clinical history. Skin testing and food-specific IgE done by standard methods are very useful, whereas oral challenges may be indicated in some situations. Majority of the patients outgrow their allergies to milk, soy, egg, and wheat, and some to peanut also, therefore, patients should be periodically reassessed. Novel diagnostic techniques which detect specific allergenic epitopes have been developed. Several newer therapies are promising.     

Bending Strength of Wood Treated with Propolis Extract and Silicon Compounds

The modification of wood and its treatment with various preservatives may affect its mechanical properties, hence the knowledge of the character changes in wood caused by impregnation is of great importance. Therefore, the aim of the research was to determine the effect of impregnation, with the propolis-silane preparation (EEP-MPTMOS/TEOS) consisting of the propolis extract (EEP) and silicon compounds: 3-(trimethoxysilyl)propyl methacrylate (MPTMOS) and tetraethoxysilane (TEOS), on the bending strength of treated wood. Moreover, in the study wood treated with components of the propolis-silane formulation was used, namely 70% ethanol, the propolis extract, and silanes (MPTMOS/TEOS). In order to determine whether the impregnation of wood affects its long-term bending, creep tests were performed depending on the humidity. The impregnation of wood with the propolis extract and the propolis-silane preparation (EEP-MPTMOS/TEOS) contributed to the increase in modulus of rapture and work to maximum load values compared to the untreated wood. In dry wood condition, the wood treated with EEP and EEP-MPTMOS/TEOS was characterized by lower modulus of elasticity values than the control samples. In turn, in wet wood condition, wood treated with the propolis-silane preparation showed an increase in the MOE value. Moreover, the impregnation of wood had an influence on the wood creep process under bending loads. The treated wood was characterized by higher relative creep compliance than the untreated wood. The exception was the wood impregnated with EEP-MPTMOS/TEOS, which showed comparable relative creep compliance to the control samples. The presented results indicate that wood treated with a bio-friendly preparation based on propolis and silicon compounds can be used in various application and also in variable humidity conditions.     

Benzalkonium Chloride: A Bronchoconstricting Preservative in Continuous Albuterol Nebulizer Solutions

For convenience, many pediatric hospitals are preparing solutions for continuous nebulized albuterol using the 0.5% 20‐ml multidose albuterol dropper bottle. This product contains benzalkonium chloride (BAC) that, by itself, produces bronchospasm that is dose dependent and cumulative. The bronchoconstrictive effects of BAC are greater in patients with more severe airway obstruction and increased airway responsiveness. Use of BAC‐containing albuterol during severe acute asthma exacerbations may antagonize the bronchodilator response to albuterol, prolong treatment, and increase the risk of albuterol‐related systemic adverse effects. Such a deleterious effect of BAC is difficult to detect because some patients improve slowly or may even worsen during treatment. We recommend that only preservative‐free albuterol products be used.