Described herein are systems and methods for personalized detection of an allergic reaction of a user. In one embodiment, a system includes an inward-facing head-mounted thermal camera (CAM) and a computer. CAM takes thermal measurements of a region on the nose (THN) of a user. The computer generates feature values based on THN and utilizes a model to detect an allergic reaction of the user based on the feature values. The model is trained based on previous THN of the user taken during different days. Some embodiments may utilize additional thermal cameras that take thermal measurements of other regions on the face, which may be utilized by the computer to generate additional feature values that are used to detect the allergic reaction. In some cases, detection of the allergic reaction may occur following a rise in nasal temperature, even before the user becomes aware of the allergic reaction.