Food allergy is an important problem in the paediatric population. Food products that are most likely to induce allergic reactions include cow’s milk, wheat, peanuts, hen’s eggs, fish and seafood. Food-allergy-related diseases include, among other things, atopic dermatitis, urticaria and asthma. Anaphylactic shock is the most severe form of allergic reaction. Intramuscular adrenalin at a dose of 0.01 mg/kg body weight (maximum dose 0.3–0.5 mg) is the primary treatment for anaphylaxis. An elimination diet is the treatment of choice in food allergy. If symptoms persist despite dietary intervention, extended diagnosis using skin prick tests and/or specific IgE measurements should be performed. We present a clinical case of a 2.5-year-old boy with erythroderma secondary to atopic dermatitis, who was referred to our Department due to the lack of improvement after outpatient treatment. It was found during hospital stay that the symptoms were caused by potato allergens.