Minoxidil has been the gold standard for topical hair loss treatments since the Food and Drug Administration (FDA) first approved the treatment for men’s hair loss in 1988.
While the 5 percent solution does offer male users up to 40 percent regrowth, there are side effects that should be considered before adding minoxidil to your hair loss regimen (1).
Minoxidil therapy is a bit less effective for women with Androgenetic Alopecia (AGA), with approximately 50 percent of female users seeing minimal hair regrowth and only 13 percent experiencing moderate hair regrowth (2)
To make it easy for you to decide whether or not minoxidil is right for you, we’ve compiled a comprehensive overview of the product, including both common and rare side effects.
The History of Minoxidil
When drug manufacturer Upjohn created minoxidil to treat ulcers, they found that a side effect of the drug was that it effectively lowered blood pressure (3).
Found to be a powerful vasodilator — a drug that widens, or dilates, your blood vessels — minoxidil was approved by the FDA in 1979 as an oral treatment for high blood pressure. It was then released in prescription-only tablets marketed under the name Loniten.
Soon afterward, patients taking Loniten for high blood pressure noticed increased hair growth and thickness as a side effect of the drug, so Upjohn undertook research to see if the product might be used to treat hair loss (4).
By 1988, the FDA had approved a 1 percent solution of minoxidil, trade-named Rogaine, to treat hair loss in men. The 1 percent solution was approved for women in 1991, and a stronger 5 percent formula was approved for both men and women in 1997.
How Minoxidil Works
Currently, there’s no real consensus on how minoxidil contributes to hair regrowth.
Some hypothesize that as a vasodilator, minoxidil increases blood flow and circulation to the scalp, bringing necessary nutrients and oxygen to hair follicles.
Other researchers think that minoxidil inhibits prostaglandins, thereby slowing or reversing hair loss. Prostaglandins, specifically the prostaglandin D2, have been shown to inhibit hair growth and are found in elevated levels in the scalps of men with androgenetic alopecia (5, 6).
Some scientists theorize that minoxidil works directly to block androgens from androgen-sensitive hair follicles and it may also delay the aging of matrix cells to prolong the anagen phase of hair growth (7).
No matter what the mechanism, minoxidil can provide hair regrowth for up to 40 percent of users, and studies show it is dose-dependent — meaning higher doses (5 percent versus 1 percent) result in more hair growth in individuals that respond well (1, 8).
The Side Effects of Minoxidil
The fact that minoxidil is a topical drug, applied to your largest organ, your skin — specifically, the skin of your scalp — means you should be aware of potential side effects.
Your skin is a conduit — and barrier — to many substances (9).
In fact, the Center for Disease Control (CDC) notes that most dermal absorption of substances centers on the outer skin layer, the stratum corneum, which is where you apply most topical products, including minoxidil (10).
Chemicals and other substances absorbed by skin travel from areas of high concentrations to areas of lower concentrations, which means anything absorbed by your skin might have systemic effects.
So let’s take a look at the wide range of side effects associated with minoxidil.
General Side Effects
The most common side effects of minoxidil use include (4):
- Scalp redness
These side effects are mostly associated with contact dermatitis, a condition brought about when a hazardous or allergy-causing substance causes an inflammatory response in your skin (11).
Contact dermatitis is characterized by redness and itching and generally goes away once you stop using whatever is causing the rash — in this case, minoxidil. It will take about two to four weeks after you discontinue use for your body to clear the rash and return to normal.
Normally, contact dermatitis is aggravated by an allergen — a substance that causes your immune system to react strongly. In the case of minoxidil, both the drug and its carrier substance, a mixture of alcohol and propylene glycol, can be the culprit.
Propylene glycol is considered to be a skin irritant, and alcohol has known skin-drying properties (12). Propylene glycol has also been shown to have the potential to cause renal toxicity and liver damage (13, 14).
These two substances, alcohol and propylene glycol, can also contribute to the increase of seborrheic dermatitis some people experience when using Minoxidil (6).
Minoxidil foam does not contain propylene glycol, so it’s a good choice for those that experience an allergic reaction to the serum formula.
Seborrheic dermatitis shows up as greasy, red skin patches that are covered by white scales or yellowish crusts. These scaly changes in the skin of your scalp are often accompanied by itching and flaking, both of which can range from mild to severe.
Like the other common side effects, seborrheic dermatitis disappears within weeks of discontinuing use of topical minoxidil.
Another common side effect of topical minoxidil, hypertrichosis, is most often seen in women and adolescents, although it appears in men as well (15). Hypertrichosis is the excessive growth of hair, and it normally appears where you don’t want it.
With topical minoxidil use, the excess hair is most common on the face — cheeks, chin, and forehead — although it can become generalized, with hair spreading down the back and limbs (16).
Fortunately, the excess hair growth will go away once you’ve stopped using minoxidil, although not for several weeks. In some cases, it may also stop after you’ve been using the topical for a prolonged period of time.
Facial Swelling and Water Retention
Edema, or swelling of the face can occur with topical minoxidil use. While this side effect has been studied, no conclusion was reached regarding danger associated with its occurrence (17).
However, given that edema can be connected with adverse cardiac events, it’s best to seek a doctor’s advice if you are having swelling of any kind after beginning minoxidil therapy (18).
Minoxidil can also cause overall water retention by causing your body to retain sodium (19). This retention can manifest as a puffy face, more pronounced eye bags, bloated hands and feet, or overall body swelling and weight gain.
Cardiovascular Side Effects
Patients with heart disease or underlying cardiovascular conditions should not use minoxidil, as it is associated with several negative cardiovascular side effects (20).
Always talk to your physician before beginning topical minoxidil therapy to avoid hazardous side effects and discontinue therapy immediately if you experience any serious adverse reaction.
Left Ventricular Enlargement
In some patients with high blood pressure, treatment with minoxidil resulted in left ventricular hypertrophy, meaning an enlarged and thickened wall of your left ventricle (21).
This enlargement, in turn, can contribute to shortness of breath, syncope, palpitations, and even heart attacks. Eventually, left ventricular hypertrophy affects the heart’s ability to function normally.
Increased Heart Rate
Minoxidil has been shown to increase the average beats per minute as well as the volume of blood flow through the arteries (20). While this may not impact someone with a healthy heart, those with cardiac disease might want to steer clear.
This is a very serious side effect, and involves an inflammation of the membrane surrounding the heart (22). As it progresses, the lining can fill with fluid, leading to pericardial effusion.
Eventually, the fluid interferes with the heart’s ability to effectively pump to circulate blood and requires immediate emergency treatment by withdrawing the fluid from the sac with a needle.
This is why you must see a physician immediately if you experience any heart-related symptoms while using topical minoxidil. If you think you may be experiencing an adverse side effect, discontinue use of minoxidil immediately.
Other Systemic Side Effects
There are conflicting studies that both prove, and disprove, the systemic side effects of topical minoxidil (23, 8). It’s important to note that there have been documented instances of systemic problems directly connected to the use of the topical formula.
While rare, sudden weight gain, swelling in the legs or ankles, local or all-over swelling, racing heart, dizziness, chest pain, or fainting all point to a severe systemic reaction and should be reported to a doctor immediately (23).
Other potential areas of concern are:
Minoxidil has been tapped as a possible contributor to ischemic optical neuropathy resulting in blurred vision that was corrected once the topical minoxidil was discontinued (24).
This is an extremely rare side effect.
Increased aminotransferase numbers have been seen in patients using topical minoxidil (19). Elevated liver enzymes like aminotransferase are markers for increased inflammation of — or damage to — the cells in your liver (25).
However, this damage is dose-dependent, so it’s possible that it can be slowed or even stopped by using a lower minoxidil formulation (26).
There have been cases of gastrointestinal distress relating to the use of topical minoxidil (27). The most common side effect is nausea, but diarrhea and vomiting were also noted.
Topical minoxidil therapy has been associated with dizziness, numbness, and syncope (becoming off-balance).
A recent case study conducted by researchers in the United Kingdom noted that topical minoxidil can cause hypotension — low blood pressure — with resulting syncope, causing potential falls (28).
The researchers conclude that this study proves that topical minoxidil does have systemic effects.
Cosmetic Side Effects — Hair Loss
Besides the cosmetic issues that could occur with cases of dermatitis, facial swelling, and excess hair growth, there’s one side effect that most hair loss sufferers using topical minoxidil should be aware of — hair loss (4).
It seems counterintuitive that a product design to help you regrow your hair would cause hair loss, but in most people, that is exactly what happens when beginning topical minoxidil.
Minoxidil’s ability to open potassium channels and widen blood vessels causes oxygen, blood, and nutrients to saturate hair follicles (4).
This mechanism can promote shedding of follicles that are in the telogen phase of growth. In effect, minoxidil re-synchronizes hair phases, which can result in sudden, but hopefully temporary, thinning.
The shedding generally begins in the first two to eight weeks, but begins to slow shortly thereafter, once your hair is acclimated to the therapy.
If you are concerned, or your shedding does not subside after two months, you’ll want to see an expert in hair loss and/or your physician to rule out other causes of hair loss such as endocrine disorders, autoimmunity, or other underlying diseases.
Still, it’s important to be aware, and prepared, for your hair to look thinner at the beginning of minoxidil therapy.
Side Effects of Stopping Minoxidil
If you need to stop using minoxidil due to allergic reactions or other health concerns, you may experience the side effect of hair loss.
Minoxidil, while stimulating hair growth, does not reduce dihydrotestosterone (DHT) or 5-alpha reductase, the enzyme responsible for the accumulation of DHT around the hair follicle (29).
Since these substances are believed to be the primary cause of male pattern baldness, once minoxidil treatment is stopped, all the hair growth that was being stimulated by the drug will be lost to acute telogen effluvium (30).
Acute telogen effluvium can be devastating, as it is a severe shed of short duration. This sudden loss of hair can cause extreme psychological stress and contribute to depression and a decline in mental health (31).
What Are the Odds of Experiencing Side Effects?
In an Upjohn (the manufacturers of Rogaine) study published in 1988, researchers were particularly keen to understand the possible risks associated with using topical minoxidil (32).
A total of 2,326 patients participated in the study from 27 different medical/research centers.
The most common side effects of topical minoxidil were medical in nature. They included headache, edema, dizziness, syncope, visual disturbances, altered taste, impotence, and cardiovascular changes. However, they only occurred in 18 percent (or just 418 participants) and were experienced at various degrees of severity.
Dermatologic effects occurred in 13.6 percent of participants (136 participants total), and they included itching, burning sensation, erythema and flushing, scaling and follicultis.
In that same year, a study was also carried out on the effects of 3 percent minoxodil solution in women (33).
The side effects in this study were also found to be minimal.
Preventing Minoxidil Side Effects
Minoxidil is generally well-tolerated, but it still has a range of side effects from mild discomfort to serious heath issues.
In fact, it’s contraindicated for many populations, such as (34):
- Pregnant and nursing mothers;
- Children and adolescents;
- People over the age of 65 (as it’s not been studied);
- Those with poor cardiac health, including high blood pressure, low blood pressure, or heart disease;
- Anyone with an allergy to propylene glycol or alcohol. People with other allergies should consult a physician first;
- Those with kidney or liver disorders; and
- Anyone with irritated, broken, inflamed, or sunburned skin on the scalp.
Anyone with the above conditions should avoid use, or speak with their doctor before using.
It’s also important to remember that the side effects experienced by minoxidil users are often dose-dependent. This means that lower doses of the topical – including 1 percent and 2 percent formulations – will be likely to produce less side effects while still delivering positive results.
One study, performed in 2002, compared the effects of 5 percent topical minoxidil versus 2 percent topical minoxidil in men with AGA (35).
The study confirmed that a higher percentage formulation was more effective in increasing hair regrowth and “the magnitude of its effect was marked (45% more hair regrowth than 2% topical minoxidil at week 48).”
There was an increased occurrence in pruritis (itching) and localized irritation, though, in the 5 percent group when compared with the 2 percent group.
This indicates that if a higher percentage formulation is causing problems, you may have success in combating side effects by reducing the percentage.
If you intend to stop minoxidil use, it’s also best to wean yourself slowly. This will reduce the severity of telogen effluvium that you experience, though it’s still expected to take place for the vast majority of people.
There is no recommended weaning schedule, though it’s best to wean yourself from the topical over the course of a few weeks or months.
For example, use your minoxidil as instructed every other day instead of every day for two weeks. You can then switch to every third day for two weeks, and continue this pattern until you’ve weaned yourself completely.
Of course, this method isn’t possible if you’re stopping due to allergic reaction or severe adverse side effect.
If you continue to suffer from side effects of the lowest percentage of minoxidil, you may also consider alternative treatment options including finasteride and dutasteride.
Why Minoxidil Is Not the Only Answer
Besides its potential for adverse side effects, minoxidil doesn’t address the root cause of hair loss.
DHT, which has long been targeted as a cause of male pattern hair loss, is definitely a factor. But it’s the inflammation that DHT causes that is the instrument behind the miniaturization, and eventual loss, of your hair (36).
And studies have shown that cytokines, the pro-inflammatory substances our bodies produce in response to stress — whether physical or mental — are a significant contributing factor to hair loss (37).
And this stress can contribute to tension in the scalp muscles, which further inhibits the growth of hair by promoting androgen sensitivity in the dermal papilla surrounding hair follicles (38).
That’s not to say that minoxidil cannot help. After all, it may increase blood flow to the scalp which is crucial to delivering oxygen and nutrients.
But a lack of blood flow to the scalp is caused by many previous factors in the hair loss framework. And it’s important to target these – which topical drugs cannot successfully do – to treat the root cause of the issue.
So, what’s the hair loss framework?
The framework is a method that attempts to pinpoint the exact cause of hair loss, while also explaining the place of various other factors and contributors.
In short, there are two main causes that contribute to hair loss: chronic inflammation, and hormonal imbalance.
These, in turn, can be caused by a variety of factors, including lifestyle (how much you exercise, whether you smoke/drink, etc.), diet, microbiome, and scalp environment.
The result of these two main causes are, essentially, the triggers of hair loss that researchers have been studying for years.
For example, inflammation has been shown to initiate calcification and this increase in calcified tissues can then lead to further inflammation (39). And estrogens (and their imbalance) may also be closely linked to Androgen Receptor (AR) activity and the production of DHT (40).
With calcification and fibrosis increasing as a result of the above mechanisms, it’s clear then why poor blood flow, low oxygen levels, and, ultimately, hair loss occur.
As mentioned, topicals such as minoxidil can only increase blood flow to the scalp but they do not target the causes of that poor blood flow (i.e. scalp DHT, androgen receptor activity, and imbalanced calcification receptors).
There are oral drugs, though, that can target scalp DHT which means they take place earlier in the hair loss framework and, therefore, may be more effective.
So you might want to consider these options, either as an alternative to or in conjunction with minoxidil.
Finasteride is a prescription medication that is primarily used in the treatment of Benign Prostatic Hyperplasia (BPH). This age-induced condition results in an enlargement of the prostate gland, which results in frequent, and often difficult, urination.
Finasteride works by reducing the amount of DHT within the prostate by inhibiting the enzyme 5-alpha-reductase (41). This leads to a reduction in prostate size and an improvement in related symptoms including frequent urination and incomplete emptying of the bladder. And while some sexual side effects are possible (though the risk is minimal), this drug does have one beneficial side effect: hair growth (42).
This was first discovered during the trial phases of FDA approval, and it has since been proven in numerous studies. One such research paper, published in 1998, outlined two one-year studies that consisted of 1553 men total (43).
The studies showed significant increases in hair count, as well as appearance of hair and slowed hair loss.
And when 1215 of these men agreed to continue on the drug for an additional one year, they continued to see marked improvement in hair growth with minimal adverse effects.
The most obvious reason for this success is its ability to indirectly reduce DHT levels within the scalp. For example, “a daily oral finasteride dose of one milligram reduces scalp DHT by 64% and serum DHT by 68%” according to a 1999 study (44).
And while we know that DHT isn’t the only cause of pattern hair loss, it does play a significant role.
Dutasteride is another drug used in the treatment of BPH, but one that which may be more effective at inhibiting two types of 5-alpha-reductase (Type I and Type II) whereas finasteride is only able to inhibit one type (Type II) (45). This was proven in a 2004 research study, which showed a marked decrease in DHT levels in individuals taking dutasteride (98.4 percent) when compared with those taking finasteride (70.8 percent) (45).
This drug, then, works similarly to finasteride by indirectly reducing DHT levels which are believed to trigger hair loss in those with a genetic predisposition to AGA. However, it’s also believed to be more effective and with only a slightly increased risk of side effects (46).
But it’s also seemingly quite effective at regrowing hair and keeping pattern hair loss at bay.
Topical minoxidil can help regrow small amounts of hair, but it’s not without potential side effects. Although most are considered mild and will go away once you’ve stopped using minoxidil, there are some severe — and dangerous — side effects.
Plus, if you stop using minoxidil, you’ll lose any regrowth you’ve experienced.
And minoxidil does not address all causes of hair loss, like stress or underlying diseases, such as hypothyroidism, among others.
While it may help some people regrow hair, you should always consult your physician before beginning minoxidil topical therapy.
And remember that alternative treatments, including finasteride and dutasteride, also exist.