Food-Induced Skin and Mucosal Pruritus: Clinical Characteristics, Pathophysiology, and Recommendations

When I saw the title of this article I was terrified. I spend inordinate amounts of time convincing patients that their itch is not being caused by foods. Gil Yosipovitch is the itch expert in the world though, and I thought maybe I was wrong, and foods did cause itch, and I'd been missing it for years.

Thankfully, this is a review of entities in which foods cause a rash that is itchy, and most are things that the majority of dermatologists are already aware of:

1. IgE-mediated food allergy can present as anaphylaxis but is extremely rare as a cause of chronic spontaneous urticaria.
2. IgE-mediated food allergy can present as oral allergy syndrome — immediate itching and mild swelling of the mouth and throat upon eating relevant foods.
3. Histamine intolerance: Patients with a relative deficiency of the GI enzyme "diamine oxidase" who can get itching from foods that have high levels of histamine — mainly fermented foods, wine, and aged meats or cheeses. This is supposedly common, but I've only found diamine oxidase supplements helpful in 1 patient over 20 years of caring for itch and dermatitis patients.
4. Fixed food eruption: Same idea as a fixed drug eruption, but triggered by a food rather than a drug — may be the answer when you see what looks like a fixed drug, but there aren't any prescription or OTC meds. A food diary helps here.
5. Dermatitis herpetiformis: We're all familiar with this one already.
6. Food -triggered atopic dermatitis: Does happen in kids under age 6, very controversial if it ever happens in adults (I don't think it does).
7. Systemic contact dermatitis: Reactions to ingestion of foods high in nickel (legumes, oatmeal, peanut butter in particular) is a very well–documented entity that likely affects about 1% of the population and triggers nonspecific dermatitis and itch. It can be diagnosed via a positive nickel patch test followed by improvement while following a low-nickel diet. In my experience, this is one of the few situations in which  patch testing can lead to clearance of a widespread, nonspecific dermatitis. My favorite resource for a low-nickel diet can be found by googling this: Rebelytics Low Nickel Diet.