Contact allergy is one of the most common forms of allergy caused by exposure to chemical or natural compounds and is the resulting response to haptens by our immune system, which performs both innate and adaptive activity (1).

It is an immune reaction that the scientific literature divides into four categories, the most common of which are:

Type I

Immediate hypersensitivity. Involves antigen binding to IgE immoglobulin antibodies 

• Atopic: atopic dermatitis, asthma and others
• Allergic: urticaria, food allergies and others

Tipo IV 

Delayed hypersensitivity. Involves T lymphocytes that play a key role in the immune system and are co-responsible for the secretion of cytokines

• Contact dermatitis and others

The risk of developing a contact allergy is highest in children after the age of five, with nickel being the main risk in females (2).

References_____________________________________________________________________

(1) Cavani, A., De Pità, O., & Girolomoni, G. (2007). New aspects of the molecular basis of contact allergy. Current opinion in allergy and clinical immunology, 7(5), 404-408.

Abstract. Purpose of review: The aim of the review is to provide an up-to-date scenario of the mechanisms governing contact allergy, a widely diffused immune response to small chemicals (haptens) penetrating the skin. Recent findings: The availability of animal models for contact allergy, such as murine contact hypersensitivity, is of great importance in understanding the pathomechanisms of the allergic response, although all these findings need confirmation in humans. Contact allergy is the result of the activation of both innate and adaptive immunity in response to haptens. Both skin resident cells, such as keratinocytes and mast cells, and immigrating leucocytes, including T lymphocytes and natural killer cells, actively participate in the reaction. Different types of T-regulatory cells appear to be crucial in the prevention of contact allergy or in the early termination of the reaction. Understanding the mechanisms that regulate immune responses to haptens is critical for the development of innovative therapeutic approaches. Summary: Although contact allergy is predominantly a T-cell-mediated disease, humoral immune responses and innate immunity actively participate in the initiation and expression of the allergic disease.

(2) Giordano‐Labadie, F., Rance, F., Pellegrin, F., Bazex, J., Dutau, G., & Schwarze, H. P. (1999). Frequency of contact allergy in children with atopic dermatitis: results of a prospective study of 137 cases. Contact dermatitis, 40(4), 192-195.

Abstract. The aim of our study was the evaluation of contact sensitization in pediatric patients with atopic dermatitis (AD). It seems that the frequency of contact allergies in the course of AD, and also the frequency of contact allergies in children, is underestimated in general. Our study has been performed by investigating 137 children with AD. The childrens' history was taken according standardized consultation guidelines and followed by a physical examination. Patch testing was performed systematically, including the European standard series, together with tixocortol pivalate, budesonide and the applied emollient. If necessary, optional patch tests were performed according to the child's history. The results demonstrate contact sensitization in 43% of all children tested. The most frequent contact allergens are: metals (19.3%), fragrance (4.4%), balsam of Peru (2.6%), lanolin (4.4%), neomycin (2.6%) and emollients (2.6%). No contact sensitization to corticosteroids nor any induction of active sensitization were seen. Statistical analysis demonstrates that the risk of developing a contact allergy is significantly elevated in children after the age of 5 years. Female sex is a risk factor only for nickel. Age of onset of AD or its severity is not associated with the development of contact allergy. In conclusion, the results indicate the necessity of performing systematic patch testing in the investigation of allergies in children with AD. Preventive measures from an early age are suggested to avoid exposure to the most frequent contact allergens.