Late cutaneous reactions to common allergens in patients with delayed pressure urticaria

In 13 patients with delayed pressure urticaria (DPU) and in seven patients with chronic recurrent urticaria (CRU), prick tests were performed with a large battery of common allergens, including food extracts. Seven patients with DPU and all patients with CRU had positive early cutaneous reactions (15 min) (ECR), while six of the DPU and only one of the CRU patients had positive late cutaneous reactions (6h) (LCR). In the CRU patients, food allergens caused a positive ECR in one and no LCR in any of the cases, while two DPU patients had ECR and four had LCR to food allergens. The one patient with CRU and a positive LCR reacted to fungi, while of the DPU patients, five had LCRs to fungi, two to other inhalants, three to NaCl and one to histamine. None of the DPU patients lost their delayed pressure reactivity while on a diet lacking the food allergens to which they gave positive reactions. These results show that DPU patients have more frequent LCR than do CRU patients. They do not, however, confirm earlier reports claiming that the majority of DPU patients are allergic to food allergens and that their disease can be cured by elimination of the offending agents from their diet.