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Allergic conjunctivitis: a comprehensive review of the literature
Italian Journal of Pediatrics 2013, 39:18 doi:10.1186/1824-7288-39-18
http://www.ijponline.net/content/pdf...7288-39-18.pdf
Note: This is a full text, free article. Read the whole article, but here are a few interesting snippets:
Italian Journal of Pediatrics 2013, 39:18 doi:10.1186/1824-7288-39-18
http://www.ijponline.net/content/pdf...7288-39-18.pdf
Note: This is a full text, free article. Read the whole article, but here are a few interesting snippets:
Contact allergy
Contact allergy, or allergic contact dermatitis, is not an IgE-mediated allergy, and can be considered in a different category than the before mentioned allergic conditions [24].
It is a type-IV delayed hypersensitivity response, that occurs through interaction of antigens with Th1 and Th2 cell subsets followed by release of cytokines [25].
It consists of two phases: sensitization (at the first exposition to the allergen, with production of memory T-lymphocytes), and elicitation of the inflammatory response (at the re-exposure to the antigen, mediated by the activation of memory allergen-specific T-lymphocytes).
Contact allergy, or allergic contact dermatitis, is not an IgE-mediated allergy, and can be considered in a different category than the before mentioned allergic conditions [24].
It is a type-IV delayed hypersensitivity response, that occurs through interaction of antigens with Th1 and Th2 cell subsets followed by release of cytokines [25].
It consists of two phases: sensitization (at the first exposition to the allergen, with production of memory T-lymphocytes), and elicitation of the inflammatory response (at the re-exposure to the antigen, mediated by the activation of memory allergen-specific T-lymphocytes).
Allergens are generally simple chemicals, low molecular weight substances that combine with skin protein to form complete allergens. Examples include poison ivy, poison oak, neomycin, nickel, latex, atropine and its derivatives.
Contact allergy involves the ocular surface, eyelids and periocular skin,
Although contact allergic reactions usually occur on the skin, including the skin of the eyelids, the conjunctiva may also support contact allergic reactions. Initial sensitization with a contact allergen may take several days. Upon re-exposure to the allergen, an indurated, erythematous reaction slowly develops. The reaction may peak 2–5 days after re-exposure.
The delay in development of the reaction is due to the slow migration of lymphocytes to the antigen depot. The term ‘delayed hypersensitivity’ is sometimes given to these reactions, in contrast to ‘immediate hypersensitivity’, a term which emphasizes the rapid development of IgE antibody-mediated reactions. Contact allergic reactions are generally associated with itching. Treatment consists of withdrawing, and avoiding contact with allergen. Severe reactions can be treated with topical or systemic corticosteroids [6].
Contact allergy involves the ocular surface, eyelids and periocular skin,
Although contact allergic reactions usually occur on the skin, including the skin of the eyelids, the conjunctiva may also support contact allergic reactions. Initial sensitization with a contact allergen may take several days. Upon re-exposure to the allergen, an indurated, erythematous reaction slowly develops. The reaction may peak 2–5 days after re-exposure.
The delay in development of the reaction is due to the slow migration of lymphocytes to the antigen depot. The term ‘delayed hypersensitivity’ is sometimes given to these reactions, in contrast to ‘immediate hypersensitivity’, a term which emphasizes the rapid development of IgE antibody-mediated reactions. Contact allergic reactions are generally associated with itching. Treatment consists of withdrawing, and avoiding contact with allergen. Severe reactions can be treated with topical or systemic corticosteroids [6].
Giant papillary conjunctivitis
Giant papillary conjunctivitis (GPC) is an inflammatory disease characterized by papillary hypertrophy of the superior tarsal conjunctiva; the appearance is similar to vernal conjunctivitis [30], but there is no significant corneal involvement (Figure 6).GPC is not an allergic disease; the incidence of systemic allergy in GPC patients is similar to that of the general population, and the stimuli for the papillary conjunctival changes are inert substances rather than allergens. For example, GPC may be caused by limbal sutures, contact lenses, ocular prostheses, and limbal dermoids [31]. When these irritative stimuli are removed, the conjunctival papillary changes resolve. The conjunctival tissues may contain mast cells, basophils, or eosinophils, but not to the extent of an allergic reaction.
Giant papillary conjunctivitis (GPC) is an inflammatory disease characterized by papillary hypertrophy of the superior tarsal conjunctiva; the appearance is similar to vernal conjunctivitis [30], but there is no significant corneal involvement (Figure 6).GPC is not an allergic disease; the incidence of systemic allergy in GPC patients is similar to that of the general population, and the stimuli for the papillary conjunctival changes are inert substances rather than allergens. For example, GPC may be caused by limbal sutures, contact lenses, ocular prostheses, and limbal dermoids [31]. When these irritative stimuli are removed, the conjunctival papillary changes resolve. The conjunctival tissues may contain mast cells, basophils, or eosinophils, but not to the extent of an allergic reaction.
Conclusion
The term allergic conjunctivitis is an inclusive term that encompasses different clinical entities based on the assumption that the classical Type I hypersensitivity mechanism is responsible for all clinical forms of allergic eye disease. However, IgE and non-IgE-mediated mechanisms are involved in the development of ocular allergic diseases. The multiple mediators, cytokines, chemokines, receptors, proteases, growth factors, intracellular signals, regulatory and inhibitory pathways, and other unknown factors and pathways are differently expressed in the different allergic disorders, inducing the different clinical aspects, diagnostic features and response to treatment. Therefore, a new classification system is desirable, preferably derived from the varied pathophysiological mechanisms operating in the different forms of ocular allergy.
The term allergic conjunctivitis is an inclusive term that encompasses different clinical entities based on the assumption that the classical Type I hypersensitivity mechanism is responsible for all clinical forms of allergic eye disease. However, IgE and non-IgE-mediated mechanisms are involved in the development of ocular allergic diseases. The multiple mediators, cytokines, chemokines, receptors, proteases, growth factors, intracellular signals, regulatory and inhibitory pathways, and other unknown factors and pathways are differently expressed in the different allergic disorders, inducing the different clinical aspects, diagnostic features and response to treatment. Therefore, a new classification system is desirable, preferably derived from the varied pathophysiological mechanisms operating in the different forms of ocular allergy.
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