Wheal Size Determines Results of Stick Prick Tests in Patients With Allergies

Wheal size can determine the results of a skin prick test (SPT) for detection of sensitization to common allergens, with Russian thistle and lamb’s quarter featuring the largest wheal diameter among other common aeroallergens tested in a study whose findings were published in Dermatologic Therapy.

This cross-sectional study included an analysis of SPT results from 972 patients (median age, 31 years) with allergy symptoms. Researchers selected common allergen extracts for SPT based on the type of allergic diseases as well as geographical pattern. In the study, a total of 624 patients had allergic rhinitis (AR), and 224 patients had asthma. The researchers also performed SPT with food allergens in 129 patients with atopic dermatitis (AD) and 67 patients with chronic urticaria (CU).

Approximately 80.2% of patients demonstrated allergic sensitization to 1 or more allergens. According to the SPT results, about 75% of participants had sensitization to inhalant allergens. The most common aeroallergens in this cohort included Russian thistle (52.1%) and lamb’s quarter (50.7%). These allergens also had the largest wheal diameter. In addition, the most common food allergens in patients with AD and CU were shrimp (23.6%) and peanuts (22.5%).

There was a significant difference in wheal size of lamb’s quarter between patients with asthma and AR (median, 5 vs 6 mm, respectively; P <.001). Also, the researchers noted a significant difference in wheal diameter in response to Russian thistle allergen between patients with AR vs those with AD (median, 10 vs 7 mm, respectively; P =.001).Also, there was a significant association of wheal size of SPT to Russian thistle and the frequency of AD (P =.003) and AR (P =.03).

The researchers suggest their study was limited in that they did not compare the results of SPT with in vitro techniques to assess the procedure’s accuracy.

The investigators concluded that slowing “the growth of unwanted plants, avoidance of [exposure] to allergenic weeds, and immunotherapy methods may help control the symptoms in allergic individuals.”

Reference

Shokouhi Shoormasti R, Mahloujirad M, Sabetkish N, et al. The most common allergens according to skin prick test: the role of wheal diameter in clinical relevancy. Published online December 5, 2020. Dermatol Ther. doi:10.1111/dth.14636