Minoxidil Side Effects: Shedding, Scalp Irritation and When to Stop

Short answer: Minoxidil 5%, the scalp spray we supply (Sons Minoxidil 5%), most often causes headache, which its leaflet (section 4, revised September 2026) lists as very common: more than 1 in 10 people. Itching or a rash, unwanted hair growth, shortness of breath, swollen hands or feet and sudden weight gain are common (up to 1 in 10), and it can cause reactions where you apply it, such as itching, irritation, dryness and redness of the scalp. Some men shed more hair 2 to 6 weeks after starting: the UK product information (SmPC, section 4.4) says this usually settles within a couple of weeks, and if it lasts more than 2 weeks, stop and see a doctor. Stop using minoxidil and contact a doctor straight away if you get swollen hands or feet or sudden unexplained weight gain (the leaflet lists both as common), chest pain, a rapid or irregular heartbeat, faintness or dizziness, swelling of the face, lips or throat, or redness, a rash or irritation of the scalp that does not go away. You may need urgent medical treatment. It is licensed for men aged 18 to 65 and is not suitable if you have high blood pressure.

This guide sets out what the leaflet and the Summary of Product Characteristics (SmPC) for Sons Minoxidil 5% say, as of October 2026: how common each side effect is, the temporary shed, the scalp, the heart, the questions men ask about erections, cancer and the liver, and how to lower the chance of side effects. It is about the 5% spray you put on your scalp, which is for men only, not minoxidil taken by mouth.

What are the side effects of minoxidil?

The most common side effect of minoxidil 5% is headache (very common); itching or a rash, unwanted hair growth, shortness of breath, swollen hands or feet and sudden weight gain are common. The table lists every side effect in the leaflet for Sons Minoxidil 5%, the product we supply, with how often the leaflet says it happens. The ones in the leaflet's "contact a doctor right away" list are marked.

Source: Sons Minoxidil 5% leaflet, section 4, last revised September 2026. The leaflet defines each band except rare, which the SmPC (section 4.8) defines as up to 1 in 1,000. The leaflet in your pack lists every side effect: please read it before you start.

The SmPC, the product information written for healthcare professionals, places a few of these in different bands. It lists chest pain, allergic reactions (including swelling of the face and a tight throat) and dermatitis, including seborrhoeic dermatitis, as common; palpitations and shortness of breath as uncommon; and changes in hair texture as rare. It also lists depressed mood, a faster heart rate, dry skin, flaking skin and acne-like spots, with no frequency given. Whichever band a sign sits in, the advice for the urgent ones is the same: stop using minoxidil and contact a doctor straight away.

If your mood drops while you are using it, speak to our pharmacist or your GP. Call 999 or go to A and E if you feel unsafe, or call the Samaritans free on 116 123 at any time.

How to report a side effect

Tell our pharmacist or your GP about any side effect, including one that is not in the leaflet. You can also report it to the MHRA on the Yellow Card website or app.

Is minoxidil safe?

It is a licensed medicine with the known side effects above, and it is not suitable for everyone. Sons Minoxidil 5% is licensed in the UK for moderate male pattern hair loss in men aged 18 to 65 (SmPC, sections 4.1 and 4.2), and its product information says only about 1 to 2% of what you apply is absorbed through healthy skin (section 5.2). More can be absorbed through broken or inflamed skin, through using too much, or in someone unusually sensitive, which could at least in theory affect the rest of the body (section 4.4). Its licence says it must not be used:

• if you are allergic to minoxidil or its other ingredients, ethanol and propylene glycol
• by women
• if you have high blood pressure, treated or untreated
• on a scalp that is not normal and healthy, including one affected by psoriasis or sunburn, or a shaved scalp
• under a dressing, or with other medicines applied to the scalp

The product information adds that it is not recommended under 18 or over 65, that men with heart disease or an abnormal heart rhythm should speak to a doctor before using it, and that it is only for male pattern hair loss: not for hair loss that is sudden or patchy, has no family history, or has no known cause. For patchy or sudden loss, or a red, sore or flaky scalp, see your GP first. These signs point to a cause other than male pattern hair loss.

Minoxidil 5% is a pharmacy medicine, supplied after a pharmacist consultation, no prescription required. Our pharmacy checklist asks about your age, your scalp, allergies, blood pressure, other medicines and your heart, and our pharmacist reviews your answers before your order is sent. Some answers mean we cannot supply it:

• "Do you have high blood pressure, whether or not you take medicine for it?" A yes: Minoxidil spray is not suitable if you have high blood pressure. Please speak to your GP.
• "Do you have any history of heart disease, chest pain, or irregular heartbeat?" A yes: Minoxidil may not be suitable for patients with a history of heart disease. Please speak to your GP or pharmacist before using minoxidil.
• Aged 66 or over: Minoxidil 5% is licensed for men aged 18 to 65, so we are unable to supply it to you.

You can read more about the medicine on our minoxidil page, and see both licensed hair loss medicines on our hair loss page.

Does minoxidil cause hair loss at first?

Yes, for some men, and it is temporary: the SmPC (section 4.4) says increased shedding generally starts two to six weeks after beginning treatment and settles within a couple of weeks. It says the shed is most likely due to minoxidil moving hairs from the resting phase of the hair cycle into the growing phase, so old hairs fall out as new ones grow in their place.

The British Association of Dermatologists' leaflet puts the shed in the first 4 to 6 weeks and says it comes from hair that had already reached the end of its life cycle being replaced by new growth.

How long does minoxidil shedding last?

Usually a couple of weeks. If the extra shedding lasts more than 2 weeks, the leaflet and the SmPC both say to stop using minoxidil and see your doctor. Do not use more to make up for it: the SmPC says that using more than the recommended dose, or using it more often, will not improve results.

Hair loss can have other causes too. The NHS lists an illness, stress, weight loss and a lack of iron among the causes of hair loss that may be temporary. If you have lost hair while losing weight, read does Mounjaro cause hair loss?

Why does minoxidil make my scalp itchy or flaky?

Itching is one of minoxidil's common side effects (up to 1 in 10 people), and its leaflet also lists reactions where you apply it, such as itching, irritation, pain, a rash, swelling, dry skin and redness, and sometimes flaking, which it says may be due to propylene glycol, one of the ingredients. The British Association of Dermatologists describes the same skin reactions: dryness, redness, scaling and itchiness where you apply it. That flaking is what many people mean when they ask whether minoxidil causes dandruff.

• Propylene glycol may cause skin irritation, and the alcohol in the solution may cause a burning feeling on damaged skin, the leaflet says. Our checklist asks: "Are you allergic to minoxidil or propylene glycol?"
• Never apply it to a scalp that is inflamed, infected, irritated or painful, or to cuts or open wounds.
• Minoxidil is for topical use on the scalp only. Avoid contact with eyes, broken skin, or other body areas. Wash hands after application.
• If redness, a rash or irritation of the scalp does not go away, stop using minoxidil and contact a doctor straight away: it is in the leaflet's urgent list.

Using too much can make the skin side effects worse: the leaflet says an overdose can increase itching, dryness, irritation and eczema.

Can minoxidil affect your heart or blood pressure?

It can. The leaflet lists a rapid or irregular heartbeat and chest pain as rare, faintness or dizziness as uncommon, and low blood pressure with no known frequency (the SmPC lists chest pain as common and palpitations as uncommon), and each one means stop using minoxidil and contact a doctor straight away. Swollen hands or feet and sudden unexplained weight gain, both common, are on the same list.

The product information explains why: very little minoxidil is absorbed through healthy skin, but more could reach the bloodstream through a damaged scalp or by using too much, and minoxidil swallowed by accident can cause serious heart problems. That is also why its licence rules it out with high blood pressure, treated or not, and why men with heart disease, an abnormal heart rhythm, angina or a circulation problem should speak to a doctor first.

• It can cause dizziness or low blood pressure. If it does, do not drive or use machines.
• Tell your pharmacist about every medicine you use. The leaflet names a steroid for skin conditions (betamethasone dipropionate), tretinoin for acne, anthralin for psoriasis and guanethidine, a blood pressure medicine.
• Keep it out of the reach of children. Swallowing it by accident can cause serious heart problems, and children should not touch the parts of your scalp where you have put it.

Can minoxidil cause headaches or unwanted hair on the face?

Yes to both: headache is minoxidil's one very common side effect (more than 1 in 10 people), and excessive hair growth is common (up to 1 in 10). The SmPC says unwanted hair can be caused by the solution spreading to skin other than the scalp, which is why the leaflet says to avoid the face and other areas, wash your hands after each use, and rinse any other area it touches with plenty of water.

The leaflet also says cases of extra body hair have been reported in babies after skin contact with the area where a carer had applied minoxidil, and the hair returned to normal within months once they were no longer in contact with it. Keep children away from the treated areas of your scalp. Changes in the colour or texture of your hair are listed too, with no known frequency. If headaches bother you or do not settle, tell our pharmacist or your GP.

Does minoxidil cause erectile dysfunction or other sexual side effects?

Erectile dysfunction is not listed as a side effect of Sons Minoxidil 5%: we have read its leaflet (section 4) and its SmPC (section 4.8) in full, and neither lists any sexual side effect, such as erection problems, a lower sex drive or changes in ejaculation. The SmPC also says there is no evidence of effects on human fertility (section 4.6). Unlike finasteride it does not affect hormones.

If you notice a change in your erections while using it, tell our pharmacist or your GP, so they can look into it. Any suspected side effect can be reported on Yellow Card, even one the leaflet does not list.

Finasteride, the other licensed medicine for male pattern hair loss, is a tablet with its own side effects: see our finasteride page and our guide to finasteride and minoxidil. There is not enough evidence to recommend using finasteride and minoxidil together, so we do not supply the two together as a plan. If you already use minoxidil, tell our pharmacist during your consultation so they can advise you.

Does minoxidil cause cancer or liver problems?

No cancer and no liver problem is listed as a side effect of Sons Minoxidil 5%. On cancer, the SmPC (section 5.3) says standard safety studies, including those of cancer-causing potential, reveal no special hazard for humans, and that minoxidil showed no sign of damaging genes. Tumours were seen in mice and rats, but the SmPC explains them as hormone effects found only in rodents at extremely high doses, and says they do not represent a cancer risk to humans.

On the liver, the SmPC lists no liver side effect (section 4.8) and gives no specific recommendations for people with liver or kidney problems (section 4.2). Only about 1 to 2% of what you apply is absorbed through healthy skin; most of that small amount is broken down, mainly in the liver, and it leaves the body in the urine (section 5.2). If you have a liver condition and are unsure, ask your GP or pharmacist before you start.

What happens when you stop using minoxidil?

The leaflet lists no side effect that starts after you stop, and the SmPC says about 95% of the minoxidil is cleared from the body within four days. What changes is your hair: the leaflet says that within 3 to 4 months of stopping, hair that regrew may go and the hair loss will carry on. The NHS says hair loss treatments only work for as long as they are used.

If you stop because of a side effect, check the urgent list above first. If there is no improvement after a year of use, the leaflet says to stop. How long it takes to work, and what to expect, is on our minoxidil page, and our finasteride guide covers the tablet.

How can you lower the chance of side effects?

Use it exactly as the leaflet says, on a completely dry, healthy scalp. Our minoxidil page's application guide:

• Part dry hair to expose the thinning area
• Apply 1ml to the scalp, not the hair, twice a day
• Massage gently, allow 4 hours before washing
• Wash hands thoroughly after use

Do not use more than 2ml in 24 hours, and do not try to make up for a missed application by using extra. The leaflet also says to wash your hands before you apply it as well as after, that 1ml is 10 sprays of the pump, to start in the centre of the thinning area and massage it in lightly, and to keep it away from your eyes and mouth. The SmPC adds: do not breathe in the spray mist.

• Protect the areas you treat from the sun, even when it is cloudy, and do not expose them to ultraviolet (UV) lamps.
• Do not use other medicines on your scalp at the same time, such as a steroid cream, and do not cover the scalp with a dressing.
• It is flammable. Do not use it while smoking, or near a naked flame or other heat source.

Step by step, with the timings, on our minoxidil page.

For support, Alopecia UK (alopeciaonline.org.uk) can help, and the British Association of Dermatologists has a patient leaflet.