Medically reviewed by Kristin Hall, FNP
Written by Our Editorial Team
Last updated 8/29/2022
Minoxidil is a topical medication that’s sold as a liquid and as a foam. Along with finasteride, it’s one of the most widely used and effective treatments for slowing down, stopping and reversing the effects of male pattern hair loss.
Like other medications, minoxidil has side effects. For most people, the side effects of minoxidil are mild and often get better over time.
However, it’s important that you’re aware of all of minoxidil’s potential adverse effects before you begin treatment.
Below, we’ve discussed all of the known side effects of minoxidil, as well as how common these side effects are among men who use minoxidil to treat hair loss.
We’ve also explained what you can do to reduce your risk of dealing with side effects while you use minoxidil, from applying the medication correctly to minimizing your use of other hair styling and care products that could cause irritation, itching and discomfort.
Before we get into the side effects of minoxidil, it’s important to quickly cover the basics of what minoxidil is and how it works as a treatment for hair loss.
Minoxidil is a topical, over-the-counter hair loss medication. It’s available as a liquid or form and is applied directly to the scalp in areas with noticeable signs of hair loss, such as your hairline or crown (the area at the top of your scalp).
A variety of issues can cause hair loss in men, but by far the most common cause of hair loss is damage to your hair follicles caused by the hormone dihydrotestosterone (DHT).
This type of hair loss is referred to as androgenetic alopecia, or male pattern baldness. It occurs when DHT attaches to receptors in your scalp and causes your hair follicles to slowly shrink -- a process that’s referred to as follicular miniaturization.
As your hair follicles shrink, your natural hair growth cycle changes, meaning each of your hairs spends less time in the anagen phase of the growth cycle (the phase in which the hair grows to its full length before shedding).
Minoxidil doesn’t block the effects of DHT, nor does it reduce DHT levels. Instead, it reduces the severity of male pattern baldness by extending the length of the anagen phase, giving your hairs more time to grow.
It also moves resting or inactive hairs into the anagen phase prematurely, promoting hair growth and thickness.
Finally, research suggests that minoxidil relaxes the vascular smooth muscles in your scalp and promotes extra blood flow through local blood vessels to your hair follicles, which may also help to stimulate hair regrowth.
These effects produce a noticeable improvement in hair growth that’s easy to detect in scientific studies.
For example, one study published in the journal Dermatologic Therapy found that 59 percent of balding men who used topical minoxidil showed improvements over the course of 12 months.
Other research has found that more than 80 percent of men with male pattern hair loss who use minoxidil report it as being very effective, effective or moderately effective at promoting new hair growth.
In short, minoxidil works -- a topic we’ve discussed in more detail in our guide to using minoxidil for a receding hairline.
Because minoxidil is a widely used, thoroughly tested medication, its side effects are well known amongst researchers and healthcare providers.
Depending on the formulation, the most common side effect of minoxidil is skin irritation close to or at the application site. This typically develops as a mild burning sensation or a skin rash after applying minoxidil solution or foam to the scalp.
In some cases, skin irritation from minoxidil may cause itching and scaling (the formation of dry, scale-like flakes on the skin).
Experts believe that skin irritation from minoxidil may be caused by minoxidil itself, as well as by the ingredients used in some minoxidil products.
One ingredient that’s thought to contribute to irritation is propylene glycol (PG), a synthetic liquid that absorbs water. Propylene glycol is often used in minoxidil and other topical products for its ability to enhance solubility and make it easier for the medication to reach the hair follicles.
Propylene glycol has been linked to allergic reactions, including allergic contact dermatitis, eczematous skin reaction (atopic eczema) and erythema (redness of the skin).
Another minoxidil ingredient that may cause red skin and irritation is ethanol, which is also used as a vehicle to improve solubility and absorption.
In addition to skin irritation, minoxidil can occasionally cause other side effects. These generally only affect a small percentage of minoxidil users, but can cause discomfort and inconvenience if they occur while you’re using minoxidil to treat hair loss.
Less common side effects of minoxidil include:
Inflammation around the hair roots
Increased facial hair growth
Red bumps on the skin
Some of these side effects, such as unwanted hair growth, may occur if minoxidil is applied to areas other than your scalp.
Minoxidil can also cause a form of temporary hair shedding, which usually develops during the first few months of use.
When you first start using minoxidil, you may notice that your hair looks thinner than usual, and that your hair loss appears to be accelerating.
This is caused by minoxidil’s effects on your hair follicles. Because minoxidil works by reducing the length of the telogen phase of the hair growth cycle (the phase in which hair follicles rest), it can cause your hair follicles to temporarily shed as they switch growth phases.
This type of hair loss is called telogen effluvium, and it’s a temporary issue. As your hairs enter into the anagen phase of the hair growth cycle (which minoxidil extends), they’ll start to grow at a normal pace and you’ll notice your hair becoming thicker, with better scalp coverage.
However, it’s far from uncommon for your hair to look a little “thin” for a month or two when you first start to apply minoxidil to areas with noticeable hair loss.
It’s important not to panic if you notice initial hair thinning from minoxidil. This type of hair loss isn’t permanent, and any difference in hair density from before and after minoxidil will begin to improve as your hair follicles synchronize and grow at the same time.
Some side effects may occur if you use minoxidil excessively frequently, or if you use a higher dose of the medication than recommended.
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 may include:
Blurred or altered vision
Numbness of the face, hands, and feet
Swelling of the face, hands, feet, and legs
Changes in body weight (rapid weight gain)
If you notice any of these side effects after applying minoxidil, it’s best to talk to your healthcare provider as soon as you can.
Although very uncommon, minoxidil has been linked to hypotension (low blood pressure). It’s important to tell your healthcare provider if you use medication to treat either high or low blood pressure.
It’s also important to inform your healthcare provider if you have a history of heart health issues, such as heart disease or congestive heart failure, or if you have ever experienced a heart attack or other cardiovascular event.
Although minoxidil is primarily used by men, it’s also a recognized treatment for female pattern hair loss -- a form of androgenic alopecia that can affect women.
Minoxidil isn’t recommended for use during pregnancy, as animal reproductive studies suggest that it may cause adverse effects. Because minoxidil is excreted in breast milk, using minoxidil while breastfeeding is not recommended.
While minoxidil is commonly sold as a generic medication, it’s also sold under the brand name Rogaine®.
Rogaine and minoxidil contain exactly the same active ingredient and work in the same way as treatments for hair loss. As such, the potential side effects of generic minoxidil and brand name Rogaine are identical.
According to the FDA, the most common side effects of Rogaine are itching and other types of skin irritation. These issues rarely affect your entire scalp -- instead, it’s normal to notice itching or irritation only on the treated areas.
However, Rogaine also contains alcohol, which means that you should only use it on areas that are affected by hair loss and take special care to avoid getting the liquid or foam in your eyes or other sensitive areas.
Every time you hear a commercial for a new drug, the interactions and side effects list seems to be long enough to fill a thesis.
However, when it comes to minoxidil, interactions aren’t very common. In fact, most research on minoxidil suggests that it only interacts with a small number of medications, which are generally associated with mild, transient side effects.
For example, minoxidil may interact with cyclosporine, an immunosuppressant drug that’s used to treat rheumatoid arthritis, Crohn’s disease, psoriasis and after organ transplants. When used together, these medications may cause an increase in hair growth around the body.
Minoxidil can also interact with aspirin. If you use baby aspirin at the same time as minoxidil, it may make minoxidil less effective.
Although drug interactions from minoxidil are uncommon and typically mild, it’s still important to inform your healthcare provider about any medications you currently use or have recently used before starting minoxidil treatment.
Your healthcare provider will be able to advise you about how you can safely use minoxidil as a hair loss treatment while reducing your risk of interactions and/or side effects.
Minoxidil is a safe, widely used hair loss medication, with numerous studies indicating that side effects are uncommon:
One review published in the journal Drug Design, Development and Therapy looked at a range of randomized controlled trials of minoxidil and found that side effects were largely mild.
A large-scale randomized clinical trial published in the Journal of the American Academy of Dermatology in 2002 found that both 2% and 5% minoxidil were well tolerated by men with androgenetic alopecia, without any evidence of systemic effects.
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 side effect often improves over time and almost always stops when treatment with minoxidil is ceased.
Millions of men around the world use minoxidil on a daily basis to prevent hair loss and improve hair growth.
On the whole, adverse effects are rare and minoxidil is widely viewed as one of the safest, most effective hair loss treatments on the market today.
Minoxidil generally works well on its own as a treatment for male pattern baldness. However, it’s even more effective when it’s used with finasteride, a prescription medication that’s available as a daily-use tablet.
Finasteride works by preventing your body from converting testosterone into DHT. Used daily, it can reduce DHT levels in your body by as much as 70 percent, shielding your hair follicles from DHT-related damage.
By reducing DHT levels with finasteride and stimulating growth with minoxidil, you can fight back against male pattern baldness from multiple angles.
Research shows that minoxidil and finasteride are much more effective when they’re used at the same time than when used individually.
For example, research published in the journal Dermatologic Therapy found that 94.1 percent of men with hair loss who used both medications experienced improvements over 12 months.
In comparison, 59 percent of men who solely used minoxidil and 80.5 percent of men who used finasteride on its own displayed improvements.
We offer finasteride online, following a consultation with a licensed healthcare provider who will determine if a prescription is appropriate.
We also offer a topical finasteride and minoxidil 6% spray, allowing you to access the benefits of both hair loss medications with a single product.
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 cat, make sure that you don’t 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 inside a separate room) and keep minoxidil products stored inside a safe area that’s out of reach of your pets.
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“I’m a 34 year old father of two and have been using Hims for over a year now. My hair is back to what it was in my mid twenties.”
Minoxidil is generally an easy medication to use. Our guide to applying minoxidil for hair growth covers the process of using minoxidil in more detail, but here the short and sweet version.
If you’re using minoxidil topical solution, follow the steps below:
Make sure your hair is completely dry.
Fill the dropper with 1mL of minoxidil solution,
Apply the minoxidil to the affected areas of your scalp.
Use your fingers to massage the minoxidil solution into your scalp.
Wash your hands thoroughly with soap and warm water.
If you’re using minoxidil foam, follow the steps below:
Make sure your hair is completely dry.
Dispense half a cap’s worth of foam onto your fingers.
Massage the foam into the areas of your scalp affected by hair loss.
Wash your hands thoroughly with soap and warm water.
After you’ve applied the medication, allow at least four hours for the medication to dry before covering or washing your hair.
Minoxidil solution and foam can stain clothing or linen, so make sure to wash your hands and allow the product to completely dry before touching any fabrics.
Minoxidil is a safe and effective medication for most men. However, like all medications, it still has the potential to cause side effects and adverse reactions, most of which are transient and mild.
If you’re worried about dealing with side effects while using minoxidil, or if you have a medical condition that you think may interfere with your ability to use minoxidil effectively, it’s important to talk to your healthcare provider.
They’ll be able to let you know if minoxidil is right for you and provide advice to help you use it safely to treat your hair loss.
Interested in finding out more about minoxidil? We offer minoxidil and finasteride online as part of our range of men’s hair loss treatments, with both medications available together in our Hair Power Pack.
You can also learn more about using these medications effectively in our full guide to what you should take for hair loss.