Medically reviewed by Kristin Hall, FNP
Written by Our Editorial Team
Last updated 3/22/2023
Minoxidil is one of the most widely used, FDA-approved hair loss treatments on the market. It’s used by millions of people all around the world to help fight against hair loss and stimulate new hair growth.
Like all medications, minoxidil has both primary effects and side effects, such as scalp irritation, rashes and unwanted hair growth. The good news is that minoxidil’s side effects are usually mild and can often be treated by making small changes to how you use this medication.
Minoxidil is available as a topical medication and as an oral medication. Most people affected by hair loss opt for the topical solution or foam versions of minoxidil, with oral minoxidil for hair loss still considered an “off-label” use.
Below, we’ve listed all of the known side effects of topical and oral minoxidil, as well as detailed information on how common side effects are from minoxidil use.
We’ve also explained what you can do if you develop side effects while using minoxidil to treat and prevent hair loss.
Minoxidil is a medication that’s used to stimulate hair growth. It’s available as a solution and as a topical foam. These versions of minoxidil are applied directly to areas of your scalp with hair loss, with most men applying them twice a day for optimal hair growth.
Oral minoxidil, on the other hand, is a vasodilator medication for hypertension that’s also used off-label to treat hair loss.
Unlike finasteride, another well-known hair loss treatment, topical minoxidil is available over the counter, meaning you can get it without a prescription.
This makes it an easy, convenient medication to add to your hair care routine if you suffer from a form of hair loss, such as androgenetic alopecia (male pattern baldness).
Currently, research suggests that minoxidil treats hair loss and improves hair growth by moving your hair follicles into a state of active, ongoing growth, and by improving the supply of blood to your scalp.
Sound confusing? Understanding how minoxidil fits into the hair growth process is fairly simple once you're aware of how your hair actually grows.
Every single hair on your body, from your scalp to your facial and body hair, grows as part of a multi-phase cycle that’s referred to as the hair growth cycle.
During this cycle, each hair follicle passes through a growth phase called the anagen phase, in which hair grows to its full length over the course of several months or years.
This is followed by a transition phase that’s called the catagen phase and a resting phase that’s referred to as the telogen phase. During the telogen phase, hair stops growing and is eventually replaced by new hair that grows from the same follicle, causing it to shed.
Most forms of hair loss involve disruptions to this cycle. For example, male pattern baldness can develop when your follicles miniaturize due to the effects of dihydrotestosterone (DHT), resulting in a shorter anagen phase.
Telogen effluvium, on the other hand, can occur when some or all of your hair follicles enter into the telogen phase early, causing sudden hair shedding.
Minoxidil moves dormant hair follicles into the anagen phase, meaning they start growing rather than resting. It also extends the duration of the anagen phase, meaning your hair follicles spend more time growing before each hair sheds from your scalp.
As for stimulating blood flow, research suggests that minoxidil dilates blood vessels throughout your scalp. This can improve the supply of vitamins, minerals and other nutrients that your hair follicles need to build strong and healthy hair strands.
And the best part is, according to research, this stuff actually works.
For example, a 2004 study published in the Journal of the American Academy of Dermatology found that out of the 984 men studied in a year-long survey, 84 percent who used minoxidil for hair growth rated it as either very effective, effective or moderately effective.
Because minoxidil is a widely used, thoroughly tested medication, its side effects are well known among healthcare providers and researchers.
Depending on the formulation, the most common topical minoxidil side effects are:
Skin irritation at the application site
Slight burning sensation
These adverse effects can be from minoxidil itself or a skin reaction to some of the substances commonly used in minoxidil formulas.
Many minoxidil sprays and foams contain ingredients like propylene glycol and alcohol. These ingredients are usually included to help minoxidil dissolve properly and improve absorption into your skin.
If your skin is sensitive to propylene glycol, alcohol or both substances, you may notice irritation after applying minoxidil topically.
For most people, any skin irritation from minoxidil is mild and temporary. Talk to your healthcare provider if you experience any reactions while taking minoxidil.
Your healthcare provider can perform a patch test — a type of test used to determine what substance is irritating your skin — to see if you’re prone to allergic contact dermatitis from any of the ingredients in your minoxidil foam or topical solution.
If you’re allergic to a specific ingredient, your healthcare provider might suggest using a different formulation less likely to cause scalp conditions.
In addition to the common side effects listed above, lesser-known minoxidil effects may include:
Temporary increased hair loss or hair shedding
Unwanted hair growth
If your hair looks slightly thinner than usual shortly after you begin treatment with minoxidil, don’t panic. Hair shedding often happens as minoxidil moves hair follicles into the anagen phase, and it’s a temporary issue.
Instead of worrying, it’s best to wait for three to four months to assess your hair growth, which is the normal amount of time that’s required to judge the efficacy of minoxidil.
Over time, you should notice that any temporary shedding from minoxidil slows down and fades away, with newer hairs filling in thin, low-density areas of your scalp.
Minoxidil may also cause unwanted hair growth, including on your body if it’s applied directly to a specific area. In fact, some people use minoxidil to stimulate beard growth to take advantage of this side effect.
To avoid unwanted body hair growth from minoxidil, carefully apply minoxidil liquid or foam only to your scalp. If minoxidil drips onto your face, neck or other body parts, carefully wash it away using soap and water.
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When used as directed, minoxidil is unlikely to cause significant issues. However, some topical minoxidil side effects may develop if you use minoxidil solution or foam excessively, such as by applying it more than two times per day or using too much of it on your scalp at once.
Potential side effects associated with excessive minoxidil use include:
Dizziness and/or lightheadedness
Swelling that affects your face, ankles, stomach or hands
Changes in your body weight, such as weight gain
Difficulty breathing when you’re lying down
Chest pain and/or a rapid heartbeat
In some cases, these symptoms may also develop if you use minoxidil normally. If you develop any of these adverse reactions after using minoxidil, contact a healthcare professional as soon as you can for further medical advice.
Most people with hair loss use topical minoxidil solution or foam to prevent shedding and speed up hair regrowth. However, in some cases, your healthcare provider may suggest using the oral version of minoxidil.
Oral minoxidil is typically used to treat hypertension, or high blood pressure. Although it hasn’t been approved by the FDA to treat hair loss, it’s sometimes prescribed off-label to people who don’t notice improvements from topical minoxidil, or find it difficult to apply twice a day.
Like topical minoxidil, oral minoxidil can cause side effects. These include:
Hypertrichosis (excessive body hair growth)
Tachycardia (fast heart rate)
In women, oral minoxidil has also been linked to headaches, depression, breast tenderness and lethargy (a lack of energy and/or enthusiasm).
If you’re prescribed oral minoxidil to treat hair loss and develop side effects, it’s important to talk to your healthcare provider if you develop any side effects.
Minoxidil is a safe, widely used medication, with numerous large-scale studies showing that side effects are uncommon.
For example, one review published in the Drug Design, Development and Therapy journal noted that minoxidil is generally considered an “effective and safe” treatment for hair loss.
A separate study, published in the Journal of the American Academy of Dermatology looked at the effects of minoxidil in men with pattern hair loss over a total treatment period of 48 weeks.
The researchers found that the medication was well tolerated without any evidence of systemic effects.
In short, research shows that minoxidil is safe and effective. Plus, it's also backed up by the fact that millions of men around the world use it on a daily basis to stop hair loss and stimulate new hair growth.
One last important note for the gents worried about how minoxidil might affect them between the sheets — minoxidil doesn’t cause sexual side effects, meaning you can use it without needing to worry about your sexual health and function.
Minoxidil is available as a generic medication and under the brand name Rogaine®. Rogaine is sold in a variety of strengths to treat hair loss in both men and women.
Remember what we mentioned above about propylene glycol and alcohol? Well, that all applies here, too. Since minoxidil and brand name Rogaine are made with the same active ingredients, they can cause similar side effects.
As such, you’ll want to follow the same precautions as you would with generic topical minoxidil solution or foam with Rogaine to avoid experiencing any Rogaine side effects.
TV commercials for new drugs are notorious for ending with a seemingly endless list of potential interactions.
Minoxidil, at least in topical solution or foam form, is a pleasant exception. In fact, one benefit of topical minoxidil is that it isn't known to cause any drug interactions.
This means you can use minoxidil solution or minoxidil foam to treat a receding hairline or general hair loss with plenty of confidence in its safety, even if you’re currently prescribed other medications.
However, minoxidil is contraindicated in people who’ve experienced an allergic reaction to it at any period in the past. Some clinicians also suggest monitoring your blood pressure levels and heart rate while using minoxidil, especially if you have any underlying medical conditions.
As always, even though minoxidil is sold over the counter without a prescription, it’s best to talk with your healthcare provider before using it to ensure it’s right for you.
Minoxidil is toxic to pets. In an article published in the Journal of the American Animal Hospital Association, researchers found that 56 percent of dogs and 59.7 percent of cats experienced a moderate or major illness after exposure to topical minoxidil.
The most common causes of exposure were coming into contact with a person’s skin after they applied minoxidil for cats, or discovering minoxidil in the trash or through other exploratory behavior for dogs.
Because of minoxidil’s safety risks for pets, this isn’t a medication that shouldn't be left hanging around for Mittens to knock off the bathroom sink.
If you have a pet, it’s important to take a few precautions when using minoxidil:
Keep your pet out of the room where you store minoxidil, especially when you apply it to your scalp. If you apply minoxidil in the bathroom, close the door and make sure to wash your hands thoroughly before you touch your pet.
Store minoxidil in a location your pet won’t find. Make sure not to leave your minoxidil on the countertop or your bedside table if you have a pet. Instead, store it safely inside a drawer your pet can’t get its paws into.
If your clothes or pillowcases are exposed to minoxidil, wash them. Make sure not to let your pets come in contact with sheets, pillowcases, or clothing that has been exposed to minoxidil without washing it thoroughly first.
If you currently use minoxidil for hair loss, taking finasteride at the same time can enhance your results and help you to maintain more of your hair. It may also cause improvements in your hair regrowth.
Finasteride is another FDA-approved hair loss treatment sold under the brand name Propecia.
Unlike minoxidil, finasteride works by stopping your body from converting testosterone to DHT, which is believed to be the primary androgen responsible for male pattern baldness.
DHT can attach to receptors inside your scalp and damage your hair follicles, gradually reducing your average hair diameter and contributing to male pattern baldness.
Our guide to DHT and male pattern hair loss goes into greater detail about the effects of DHT on your hair follicles, as well as how medications like finasteride prevent DHT-related damage.
In a study published in the journal Dermatologic Therapy, researchers found that finasteride and minoxidil were more likely to produce hair-related improvements when they were used together than when either medication was used on its own.
In the 428-person study, 59 percent of men with pattern hair loss who used minoxidil on its own and 80.5 percent of men who used finasteride showed improvements after 12 months.
In comparison, 94.1 percent of men who used both medications showed improvements after 12 months.
If you currently use minoxidil, adding finasteride to your hair loss prevention routine could result in a bigger reduction in hair loss and a better hair regrowth rate. But if you're curious about side effects such as acne, this guide will save you the trouble of searching, "finasteride minoxidil acne".
Minoxidil is a simple medication to apply — a topic we’ve covered in great detail in our guide to applying minoxidil for hair growth. We’ve included the short and sweet version of how to get the best result while using minoxidil below.
If you use a minoxidil topical solution, follow these steps:
Make sure that your hair is completely dry.
Fill the dropper with 1mL of minoxidil solution.
Apply the minoxidil to the affected areas of your scalp.
Using your fingers, gently massage the minoxidil solution into your scalp.
Wash your hands thoroughly using soap and warm water.
If you use minoxidil foam, follow these steps:
Make sure your hair is completely dry.
Dispense half a cap’s worth of foam onto your fingers.
Massage the foam into areas of your scalp with noticeable hair loss.
After you finish, wash your hands thoroughly with soap and warm water.
After you’ve applied minoxidil solution or foam to your scalp, allow at least four hours to pass so that the medication can dry before you cover or wash your hair.
Minoxidil can stain clothing or linen, so wash your hands thoroughly after applying the solution or foam to your scalp. Do not let your scalp touch any kind of fabric before minoxidil has dried properly.
Minoxidil is generally a safe and effective medication — one of many reasons it’s available over the counter, without any need for a prescription.
Because it’s available over the counter, minoxidil is a great first choice if you’re starting to notice the early signs of male pattern baldness and want to take action.
However, like all medications, minoxidil can still cause adverse effects. As such, it’s important to keep the following in mind when you’re using minoxidil to treat hair loss:
Most side effects of minoxidil are mild. Serious side effects from minoxidil aren’t very common. When side effects do occur, they tend to be issues like itching, irritated skin or redness.
Minoxidil doesn’t cause sexual side effects. Minoxidil has no known effects on your sex hormone levels, nor is it linked to issues like reduced sex drive, erectile dysfunction (ED) or premature ejaculation (PE).
Side effects from topical and oral minoxidil can differ. When taken orally, minoxidil may cause side effects such as fluid retention, elevated heart rate and increased body hair growth.
If you develop side effects while using minoxidil, it’s important to talk with your healthcare provider. They may suggest making certain changes to the way you use minoxidil, switching to a different minoxidil formulation or trying another hair loss medication.
Interested in using minoxidil, finasteride or other medications to stop hair loss and increase your hair count? We offer a range of evidence-based hair loss medications online, including minoxidil solution, minoxidil foam and finasteride.
You can also purchase minoxidil and finasteride together as part of our Hair Power Pack, which is available following an online consultation with a physician who will determine if a prescription is appropriate.