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Minoxidil Side Effects: What Are They and Are They Common?

Angela Sheddan

Medically reviewed by Angela Sheddan, DNP, FNP-BC

Written by Our Editorial Team

Last updated 4/29/2021

Minoxidil is a topical medication that’s used to treat hair loss. Along with finasteride, it’s one of the most widely used and effective treatment options for increasing hair growth and dealing with the effects of male pattern baldness.

Like all medications, minoxidil has both primary effects and side effects. For most people, the side effects of minoxidil are relatively minor. 

However, it’s important that you’re aware of all of minoxidil’s potential effects before you begin treatment.

Below, we’ve listed all of the known side effects of minoxidil, as well as detailed information on how common side effects are from minoxidil use.

What Are The Side Effects of Minoxidil?

Because minoxidil is a widely used, thoroughly tested medication, its side effects are well known amongst doctors and researchers.

Depending on the formulation, the most common side effect of minoxidil is skin irritation at or near the application site. In some cases, minoxidil users can develop a skin rash or experience a mild burning feeling after using minoxidil spray or foam.

This can be a reaction to the minoxidil itself or a reaction to some of the substances commonly used in minoxidil formulas. Many minoxidil products contain propylene glycol, and alcohol, which can lead to skin rash and irritation when applied topically.

Less Common Side Effects of Minoxidil

Other, less common side effects of minoxidil include:

  • Acne

  • Facial hair growth

  • Inflammation around the hair roots

  • Facial swelling

  • Increased hair loss

These side effects are relatively uncommon and do not affect most minoxidil users. Increased hair loss, one of the most publicized side effects of minoxidil, is often the result of hair follicles rapidly moving through the hair growth cycle and shedding before an anagen phase. This is normal as it is part of the mechanism in how minoxidil works.

Minoxidil Side Effects From Excessive Use

There are also side effects of minoxidil that can occur from excessive use of the medication. 

In most cases, these side effects occur when too much minoxidil is applied at once, resulting in an overly high level of minoxidil being absorbed into the body. These side effects include:

  • Dizziness

  • Lightheadedness

  • Fainting

  • Irregular heartbeat

  • Chest pain

  • Headaches

  • Flushing

  • Blurred or altered vision

  • Numbness of the face, hands, and feet

  • Swelling of the face, hands, feet, and legs

  • Rapid weight gain

If you notice any of these side effects after taking minoxidil, the best course of action is to speak to your doctor as soon as possible.

Rogaine Side Effects

While minoxidil is sold generically, it’s also sold under the brand name Rogaine®. That said, the side effects of Rogaine are virtually identical to those of minoxidil. 

According to the FDA, the most common side effect of Rogaine is itching and other skin irritation on the treated area. 

However, Rogaine also contains alcohol, which means that you should only treat the affected area with it — and take special care to avoid getting it in your eyes or other sensitive skin areas.

Other, less common minoxidil side effects include acne, inflammation around the hair roots, facial hair growth, acne, swelling around the face and even increased hair loss, in some cases.

And if used excessively, minoxidil may cause side effects like flushing of the face, chest pains, headaches and even fainting.

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Minoxidil Interactions

Every time you hear a commercial for a new drug, the interactions and side effects list seems to be through the roof. 

But, believe it or not, according to the majority of research out there regarding minoxidil, it won’t really interact with anything.

However, it’s contraindicated both in people who have had an allergic reaction to it in the past, and also breastfeeding women, as studies have observed, in very rare cases, congenital disabilities.

Is Minoxidil Safe?

Minoxidil is a safe, widely used medication, with numerous studies indicating that side effects are uncommon:

  • One study showed that people who used topical minoxidil twice daily saw no systematic side effects.

  • A longer 48 week study shows that topical minoxidil has no systemic effects, even at a higher-than-average 5% concentration.

Of the side effects of minoxidil, the most common is skin irritation in and around the area where the spray or foam is applied. This usually reverses and heals by stopping the minoxidil.

Millions of men around the world use minoxidil on a daily basis to prevent hair loss and improve hair growth. 

On the whole, side effects are rare and minoxidil is viewed as one of the safest hair loss treatments on the market today.

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Minoxidil and Pets

One point about minoxidil that’s important to note is that it can potentially be highly toxic to cats, as they lack the enzymes required to metabolize and excrete minoxidil from the body.

According to the ASPCA, there were six cases between 2001 and 2014 of cats being negatively affected by exposure to minoxidil. Of these, four cats have died after exposure, while the others required aggressive treatment in order to survive.

If you have a pet cat, make sure you do not ever directly apply minoxidil to its skin or fur. Use the minoxidil spray or foam in an isolated area (such as a bathroom, with your cat in a separate room) and keep minoxidil products stored inside a safe area that’s out of reach of your pets.

How to Properly Use Minoxidil

Minoxidil is also simple to apply. We cover this topic in great depth in our How to Apply Minoxidil for Hair Growth blog, but here’s the short-and-sweet version:

For topical solution:

  • Make sure your hair is completely dry.

  • Fill the dropper with 1mL of minoxidil.

  • Apply the minoxidil to the affected areas of your scalp.

  • With your fingers, massage the minoxidil solution into your scalp.

  • Wash your hands with warm soap and water.

For foam solution:

  • Make sure your hair is completely dry.

  • Dispense a half cap full's worth of foam onto your fingers.

  • Massage the foam into the areas of your scalp that need it.

  • Wash your hands with warm soap and water.

After you’ve applied the medication, allow at least four hours for the medication to dry before covering or washing your hair.

It’s also important to know that this stuff can stain clothing or linen, so make sure to wash your hands and make sure the product is fully dry before touching any fabrics.

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Minoxidil For Hair Loss

Minoxidil is one of the most popular FDA-approved hair loss treatments on the market, and every year, millions of people use it to their satisfaction.

However, just like most other drugs out there, it does come with some common and not-so-common side effects that you should be aware of. 

Luckily, the common side effects of minoxidil appear to be pretty light.

However, if you begin to notice any adverse reactions after you start using minoxidil or its branded name, Rogaine, the best thing to do is stop immediately and contact your healthcare provider. 

They’ll be able to help you figure out what’s going on.

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.