Skin Reaction

SKIN REACTION (cutireaction), a characteristic inflammatory change in the skin upon the application of a specific substance to its scarified areas. Sometimes it is possible to obtain a skin reaction by rubbing the same substances through the intact epidermis. Thus, Carl Spengler (K. Spengler) proposed the systematic rubbing of increasing doses of tuberculin into thoroughly disinfected skin for therapeutic purposes. Moro (Moro) uses the following ointment for diagnostic purposes: Koch's tuberculin (Alttuberkulin) 5.0 and anhydrous lanolin 5.0. A pea-sized lump of ointment is rubbed in with a finger for 1 minute over a skin surface of 5 cm². The reaction occurs after 20-30 hours. Skin reactions are widely used to determine the allergic state of the organism (see Allergy) and for the diagnosis of certain diseases (Pirquet reaction for tuberculosis, reaction with mallein for glanders, etc.). Compared to other similar reactions (subcutaneous, intradermal, nasal, and ocular), the skin reaction has the advantage of its simplicity and complete harmlessness to the subject being tested. It is performed in such a way that a drop of the substance, in relation to which the increased sensitivity of the organism (allergy) is being investigated, is applied to some area of the skin, usually on the flexor surface of the forearm or upper arm, and a superficial scratch of the skin is made through it with a scalpel or a special needle so that blood does not appear. Thus, the methodology of the skin reaction fully corresponds to that used in smallpox vaccination. Under normal conditions, i.e., in the absence of an allergic state, no reaction from the skin is observed at the site of the scratch, except for redness in the form of a narrow line, sometimes with the formation of a small scab, which does not exceed the boundaries of the inflicted trauma in its dimensions. If, however, there is altered skin sensitivity to the given substance (allergy), then following the application of the scratch, sometimes within the first few minutes, characteristic phenomena of varying intensity and duration develop, depending on the degree of the allergic state. As with all manifestations of altered sensitivity of the organism in general, the skin reaction manifests itself in exactly the same way with the most diverse allergens. Thus, the law holds full force here, stating that with altered sensitivity, only the cause inducing the allergic state is specific, while the manifestation of the reaction is identical (differs little) with the most diverse allergens. The skin method, introduced into practice by Walker, is distinguished by less sensitivity than the intradermal one, recommended mainly by Cooke, as it yields positive results in a smaller number of allergy cases, but on the other hand, it is more specific and less frequently gives a false reaction, i.e., positive results in subjects who have no clinical symptoms of an allergic state. The manifestation and development of the allergic reaction in the skin method fully correspond to those observed in the intradermal method (see Intradermal reaction).