Allergy testing is usually performed by exposing the skin to small quantities of potential allergens on the inner forearm and scratching the protective epidermis to increase exposure. After 15 minutes the dermatologist performs a visual check for swelling and erythema which is subjective and difficult for e.g. dark skin types. A small smart phone based thermo camera (FLIR One) was used to obtain quantitative images in a feasibility study of 17 patients Directly after allergen exposure on the forearm, thermal images were captured at 30 seconds interval and processed to a time lapse movie over 15 minutes. Considering the 'subjective' reading of the dermatologist as golden standard, in 11/17 pts (65%) the evaluation of dermatologist was confirmed by the thermo camera including 5 of 6 patients without allergic response. In 7 patients thermo showed additional spots. Of the 342 sites tested, the dermatologist detected 47 allergies of which 28 (60%) were confirmed by thermo imaging while thermo imaging showed 12 additional spots. The method can be improved with user dedicated acquisition software and better registration between normal and thermal images. The lymphatic reaction seems to shift from the original puncture site. The interpretation of the thermal images is still subjective since collecting quantitative data is difficult due to motion patient during 15 minutes. Although not yet conclusive, thermal imaging shows to be promising to improve the sensitivity and selectivity of allergy testing using a smart phone based camera.

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Lindi Barla, Rudolf M. Verdaasdonk, Thomas Rustemeyer, John Klaessens, and Albert van der Veen, "Use of a smart phone based thermo camera for skin prick allergy testing: a feasibility study (Conference Presentation)," Proc. SPIE 9689, Photonic Therapeutics and Diagnostics XII, 96890E (Presented at SPIE BiOS: February 13, 2016; Published: 27 April 2016); https://doi.org/10.1117/12.2213440.4828143225001.