Parents have asked me if a diagnosis of a food allergy can be made by placing the food on the skin.
The answer is, not always.
Why is that?
Not all concentrations of the allergen can lead to a reaction.
𝐂𝐨𝐧𝐭𝐚𝐜𝐭 𝐃𝐞𝐫𝐦𝐚𝐭𝐢𝐭𝐢𝐬 happens when a substance gets in contact with the skin, causing a localised reaction.
It can be either 𝘪𝘳𝘳𝘪𝘵𝘢𝘯𝘵 (80% of reactions) or 𝘢𝘭𝘭𝘦𝘳𝘨𝘪𝘤 (20% of reactions), leading to different reactions.
It affects people that deal with the substances frequently, though it can happen to anyone.
Treatment starts with avoidance of contact with the substance causing the reaction.
Following this, the creams used are very similar to the ones used in eczema.
It is not frequent the need for oral or intravenous medication.
How to make a diagnosis?
There is also a difference in signs.
Nickel can give irritant and allergic contact dermatitis.
Dr Costa is a Consultant Paediatrician and fellow of the Royal College of Paediatrics and Child Health.