You may experience a 'tingling' or 'burning' sensation when applying the serum. This is a normal reaction when using the serum. The sensation is attributed to the heating agent HotFlux, or vanillyl butyl ether. This helps rejuvenate hair growth by improving blood flow and nutrient delivery to the hair roots.
The intensity of this 'warm' feeling varies per person, from minimal noticeable to irritation. Most cases are mild, but in rare cases redness and tenderness may occur. If you experience unpleasant side effects, discontinue use and consult a doctor.