Can food trigger or exacerbate eczema symptoms in patients with eczema, and what is the pathophysiology behind these flares?

Can Food Flare Eczema and What is the Pathophysiology?

Yes, food can directly trigger eczema flares in a subset of patients, particularly in young children with moderate-to-severe disease, though this occurs in only about 35% of affected children and is less common in adults. 1, 2

Who Gets Food-Triggered Eczema Flares

Food allergies are clinically relevant triggers primarily in children under 5 years old with moderate-to-severe atopic dermatitis that persists despite optimized topical treatment. 1, 3, 2

• The most common food allergens in young children are cow's milk, eggs, wheat, soy, and peanuts 3
• In older children, adolescents, and adults, pollen-related foods become more important triggers than classical food allergens like milk and eggs 4, 5
• Tree nuts, shellfish, and fish are more common triggers in older children 3
• Adults with eczema who have food allergies typically present with immediate symptoms, with nuts and tomatoes being the major allergens 6

Pathophysiology of Food-Induced Eczema Flares

The mechanism involves both IgE-mediated immediate hypersensitivity reactions and T-cell mediated delayed responses that manifest as worsening eczema. 4, 5

• More than 50% of children with food-exacerbated atopic dermatitis will react with worsening skin eczema either alone or in addition to immediate symptoms 4, 5
• Both IgE-associated and IgE-independent T-cell mediated responses appear to be involved in clinical eczematous reactions 5
• Immediate hypersensitivity (type I) reactions to foods can occur in patients with eczema, ranging from contact urticaria to anaphylaxis 1
• The specific immunologic pathways remain incompletely understood, but the frequent finding of specific IgE antibodies to offending foods suggests immediate-type allergic mechanisms are involved 7

Critical Clinical Approach: When to Suspect Food Triggers

Do not attribute eczema flares to food allergy based on history alone—this leads to unnecessary dietary restrictions and potential malnutrition. 1, 2

The American Academy of Dermatology recommends considering limited food allergy testing only when: 1, 2

• Child is under 5 years old with moderate-to-severe atopic dermatitis
• Disease persists despite optimal topical management and adequate emollient use
• There is a reliable history of immediate allergic reaction after food ingestion

Before testing for food allergy, you must first optimize topical corticosteroid therapy and ensure adequate emollient use, as many children have inadequately treated atopic dermatitis rather than food allergy. 2

Diagnostic Algorithm

Step 1: Document temporal relationship 3

• Keep a food diary recording symptoms and intake to identify consistent correlations 1
• Look for immediate reactions versus delayed effects occurring 2-4 days after exposure 3

Step 2: Perform targeted allergy testing 1, 3

• Skin prick testing (SPT) has high negative predictive value (>95%) but low positive predictive value (40-60%) 2
• Serum-specific IgE testing can be used as an alternative, especially with widespread skin lesions 2
• Positive tests only indicate sensitization, not clinical allergy 1, 2

Step 3: Diagnostic elimination diet (4-6 weeks) 1, 2

• Only proceed if there is consistent correlation of symptoms with or without positive testing 1
• If eczema remains stable or worsens during elimination, the food is unlikely to be a relevant trigger 1

Step 4: Supervised oral food challenge 1, 2

• This is essential to confirm diagnosis, as improvement during elimination may be coincidental or placebo effect 2
• Evaluate skin status with an established score (SCORAD or EASI) at 24 hours and later, as delayed worsening will otherwise be missed 4
• Double-blind, placebo-controlled food challenge is the gold standard 2

Critical Pitfalls to Avoid

Never perform broad panel allergy testing without a clear history of reproducible reactions—positive results may reflect sensitization without clinical relevance. 3, 8, 2

Avoid multiple dietary restrictions and long-term avoidance without documented, clinically relevant food allergies, as this leads to weight loss, poor growth, calcium deficiency, hypovitaminosis, and kwashiorkor. 1, 2

Do not prescribe avoidance diets without continuing to treat the underlying atopic dermatitis with appropriate topical therapies—effective treatment remains skin care and topical corticosteroids even in confirmed food allergy. 2

A retrospective study demonstrated that 84-93% of avoided foods in children with atopic dermatitis could be returned to the diet and tolerated after proper evaluation 1

When Food Allergy is Confirmed

Referral to an allergist is essential for longitudinal care, formulation of emergency anaphylaxis action plan, supervised oral food challenges, and prevention of unnecessary dietary restrictions. 2

Most children with food allergies develop tolerance over time, requiring regular re-evaluation 2