When minoxidil was used as a popular oral treatment for high blood pressure, one of the side effects was hair growth and a seemingly reversal of male patterned baldness. That surprising symptom became the main attraction when minoxidil became the first drug approved by the FDA for treatment of hair loss. The pill version had a host of unpleasant side effects, including rapid and irregular heartbeat, lightheaded, swelling of the face and extremities, and even cardiac lesions and necrosis of the heart muscles, symptoms which may have been acceptable for the treatment of dangerously high blood pressure but weren’t for hair loss.
The topical version, however, is very safe and tests have shown no significant side effects compared to a placebo. Most patients tolerate the topical form of minoxidil well, but a few may experience mild negative symptoms, including irruption, itching, and redness of the treated scalp, burning or itching of the eyes. The alcohol present in some topical applications can dry out the scalp, possibly leading to dandruff and contact dermatitis. Although not medically documented, some patients have reported skin redness, generalized dry skin, and dark under-eye circles.
Other users may experience unwanted hair growth or thickening or darkening in other locations, including the face, chest, armpits, or legs. This can be upsetting for women, but can be treated with shaving, hair removal creams, or even electrolysis. Paradoxically, minoxidil can sometimes cause hair loss, a process often described as “shedding,” probably as the medication encourages hairs in the telogen phase to shed early.
Rarer and more severe side effects can including chest pain, dizziness, fainting, rapid heartbeat, swelling of the hands or the feet, sudden or allergic reactions including hives, rash, severe itching, difficulty breathing, tightness in the chest, swelling of the face, lips, mouth, or tongue. If you experience any of these symptoms, you should stop taking minoxidil immediately and seek emergency medical treatment.