Contact dermatitis

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.⁣

• Some reactions might be due to a 𝘊𝘰𝘯𝘵𝘢𝘤𝘵 𝘋𝘦𝘳𝘮𝘢𝘵𝘪𝘵𝘪𝘴.⁣

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.⁣

• Most commonly, it affects people working in the 𝘤𝘩𝘦𝘮𝘪𝘤𝘢𝘭, 𝘱𝘩𝘢𝘳𝘮𝘢𝘤𝘦𝘶𝘵𝘪𝘤𝘢𝘭 or 𝘣𝘦𝘢𝘶𝘵𝘺 𝘪𝘯𝘥𝘶𝘴𝘵𝘳𝘺.
• 𝘔𝘦𝘤𝘩𝘢𝘯𝘪𝘤𝘴 and 𝘩𝘦𝘢𝘭𝘵𝘩𝘤𝘢𝘳𝘦 𝘸𝘰𝘳𝘬𝘦𝘳𝘴 can also be affected.⁣

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?⁣

• It is fairly easy, as there is a good association between the contact and the onset of the reaction.⁣
• In some cases, when there is a mix of chemicals, patch testing can be used (I will speak about this in another post).⁣

There is also a difference in signs.⁣

• 𝐈𝐫𝐫𝐢𝐭𝐚𝐧𝐭:⁣

1. Blisters⁣
2. Dry skin leads to cracking⁣
3. Cracking leads to sores and crusts⁣ Swelling⁣

• 𝐀𝐥𝐥𝐞𝐫𝐠𝐢𝐜:⁣

1. Hives⁣
2. Itching⁣
3. Red skin⁣
4. Dry and flaking skin⁣
5. Swelling, especially if affecting mucosas⁣

Nickel can give irritant and allergic contact dermatitis.


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