Why do contact Skin Allergens cause break outs in other places
Contact allergens can cause break outs in other places than where we are exposed. This effect was first noticed when skin patch testing was started (2). Hand eczema or other active eczema would often get worst after the patch test. Another case is Periodical Dermatitis when exposed to topical steroids used on your hands – often cause eczema like breakouts on your face. We also see this with food additives and food allergies. Food additives that contain sulfiting agents can also have adverse reactions. Contact of the allergen in the food with specific IgE on mast cells in the gastrointestinal tract may produce local reactions or may diffuse freely to other sites such as the skin (1). The skin around the fingers elbow and knee joints are often affected. I have been asked by several patients why they have breakout around their joints, this is the answer. Often we can track this back to ingesting food allergens and exposure to contact allergens at other body sites. This is often seen in psoriasis and rosacea also. These reactions can happen quickly as an one who has had a reaction to an antibiotic like penicillin or clindamycin will tell you. With methylisothiazolinone being added to many mouth washes we are see the development Peripheral Dermatitis eczema on the face around the mouth and breakouts around the joints. On our list of known contact allergens we often show contact allergens that are added to foods to enhance the flavor or fragrance of the product. This often keeps the eczema or psoriasis from healing
References:
· Roitt’s Essential Immunology 11th Edition
· Fisher’s Contact Dermatitis 6th Edition
· Clindamycin
· Methylisothiazolinone