Is it possible to be allergic to minoxidil? What reactions would happen if one is allergic?

Most contact dermatitis (uncomfortable itching, irritation) from Rogaine Minoxidil use is because of Propylene Glycol (PG), NOT the minoxidil itself. Seek out the advice from a full-time ABHRS-certified, IAHRS-accepted hair loss specialist for a powerful, PG-free prescription alternative like Formula 82M Minoxidil. Formula 82M is more powerful than over-the-counter rogaine because of the synergistic ingredients like Retin-A retinoic acid, anti-inflammatories and sophisticated moisturizers for the hair and scalp. It's also not greasy and absorbs fast so you can use it properly (twice a day is recommended) and not have it impair your hairstyle or lifestyle. Search Formula 82M Minoxidil Alternative Reviews. Seek out a "Hair Loss ONLY" specialist who will actually measure your hair growth scientifically with HairCheck and look at your scalp with a microscope. Choose a credentialed hair restoration physician with experience with 82M and other adjunctive non-chemical hair regrowth treatments like laser, PRP+Placenta ECM, FUE hair transplants etc. in thousands of hair loss patients that is not a "jack-of-all-trades."  
Sincerely, 
Dr. Alan J. Bauman, MD, ABHRS, IAHRS, FISHRS

It is possible, but not that common. This needs an in-person evaluation.  I recommend getting a formal evaluation with a hair loss expert. There are great non-invasive options like prp/progesterone and/or hair transplantation. See an expert. Best, Dr. Emer 

Minoxidil solution is well known to cause allergies due to an ingredient propylene glycol. The foam does not contain this ingredient so it is less likely to cause allergies, but both products are safe in the majority of people. These products also have ingredients like fragrances and preservatives that can cause allergic dermatitis but those are also not common. If you are allergic to a topical product it produces a rash much like poison ivy that is red, crusty, itchy, and possibly blistered.  The more you use it, the worse the rash will get.  When you stop, the rash would go away. See a dermatologist for evaluation. They may do patch testing to verify if you have an allergy.

It is possible to be allergic to any product, including Minoxidil but this is pretty uncommon with the foam formulation. Minoxidil comes as a solution or a foam. The solution has a preservative ingredient in it (propylene glycol) which can commonly cause scalp reactions such as itching, flaking, irritation. The foam version of minoxidil does not contain this ingredient and patients tolerate it quite well. If you are using minoxidil solution, I would try switching to the foam version. if you are still experiencing these problems while using minoxidil foam, then you may just want to discontinue using minoxidil.

It is possible albeit not that common. Patients get intense redness and sometimes blisters. It can be painful! See a dermatologist to differentiate irritation from allergy and other causes of scalp redness and flaking, including seborrheic dermatitis and psoriasis.

Thank you for your question.  Allergic reactions are theoretically possible with just about any medication, cream, cosmetic, or toiletry product.  Some patients do experience allergic reactions to topical minoxidil (or one of the other, inactive ingredients in the solution) - this typically manifests as an itchy rash on the scalp and around the hairline.  It's also important to note that, much more commonly, minoxidil can cause an exacerbation of seborrheic dermatitis and dandruff, which can also result in an itchy scalp.  I hope this helps.   

Allergies to minoxidil are not uncommon. They can cause rashes, itching and sometimes low blood pressure