Minoxidil: foam or solution?

On the pharmacy shelf, two boxes of minoxidil sit side by side. One holds a solution you put on with a dropper or a spray. The other holds a foam that comes out of a pressurised can. Same molecule, same promise on the box. So which one should you pick, and does it make any difference to your scalp?

The short answer: the difference lies mostly in what comes with the molecule, and in one ingredient in particular, propylene glycol. As for results, nobody has shown that one form works better than the other.

Same molecule, two vehicles

Minoxidil is applied directly to the scalp, as a solution or a foam¹. It’s a medicine, sold in pharmacies without a prescription in France², and it isn’t reimbursed there¹. Exactly how it works isn’t fully understood¹. It acts on the hair growth cycle, waking up resting follicles.

What changes from one form to the other is the vehicle: everything that isn’t the active substance. The solutions sold in France contain water, ethanol and propylene glycol²³. The foam contains water, ethanol, glycerol, fatty alcohols and a propellant gas, but no propylene glycol⁴.

Propylene glycol, often behind the itching

The European guideline on androgenetic alopecia (known as the “S3” guideline) is clear on this: irritation is more common with the 5% solution, because it contains more propylene glycol⁵. French product labels give the exact amounts.

A 2009 review puts scalp irritation (dryness, flaking, itching, redness) at around 7% of people using the 2% solution, and higher with the 5% solution⁶.

Not every red patch comes from this. Simple irritation and contact allergy look alike, and the allergy can be to propylene glycol or to minoxidil itself. The European guideline recommends confirming it with skin allergy tests (patch tests). If propylene glycol is to blame, you can switch vehicle. If it’s minoxidil, you have to stop⁵. The foam isn’t risk-free either: its label notes that some of its ingredients can cause contact eczema⁴.

What the two key studies show

In men, the foam was first compared with a placebo. In 2007, Elise Olsen’s team tested the propylene glycol-free 5% foam in 352 men aged 18 to 49, against a foam with no active ingredient, for 16 weeks⁷. On the crown, the number of hairs (not counting fine vellus hairs) rose by 13.4% with the active foam, against 3.4% with the placebo⁵. 143 men carried on to 52 weeks so tolerance could be followed, and it was judged good⁷. The limits: results were only measured over 16 weeks, and the foam was compared with a placebo, not with the solution.

In women, it was compared with the solution. In 2011, a team in Berlin split 113 women between the 5% foam and the 2% solution for 24 weeks⁸. The foam did at least as well on hair count and thickness, with a slight edge that wasn’t statistically significant. Above all, it was better tolerated: less local intolerance, especially less itching and flaking⁸. The limit, flagged by the authors: because the two products look different, the women knew which one they were using.

Which one regrows more hair?

Neither has been shown to. The European guideline spells it out: more studies are needed to compare the solution and the foam, and it can’t recommend the 5% foam over the 5% solution⁵.

What matters more is sticking with it, and time. Dermatologists judge the effect after 6 months at the earliest⁵: it’s all explained in when to judge whether minoxidil works. And whichever form you use, heavier shedding can start 2 to 6 weeks in, then fade⁴: that’s the shedding of the first few weeks, a sign of the hair cycle restarting.

Day to day: styling, drying, applying

This is where you notice the difference most. In the trial in women, more of those on the foam felt the treatment didn’t get in the way of styling their hair⁸. The foam’s volatile ingredients evaporate in 20 to 30 seconds and leave little residue. Users who were asked liked that it didn’t drip and dried quickly⁶.

The foam has its drawbacks too. Some women find it hard to apply day to day, European dermatologists note⁵. With both forms, the label says to apply the product to dry hair and a dry scalp⁴, and to wash your hands thoroughly afterwards³.

In France, who can use what

The studies tested the foam in women. But in France, the product labels draw a clear line:

• the 2% solution is for adults, men or women²;
• the 5% solution is for men and is contraindicated in women³;
• the foam, which only comes in 5%, is for men and must not be used by women⁴.

A dermatologist may make a different choice for your situation after examining you: that’s their job. Without medical advice, stick to the label. Minoxidil is contraindicated in pregnancy¹ and should be avoided while breastfeeding². If you’re a woman and your hair is thinning, start with what we know about hair loss in women.

Foam or solution, talk to your pharmacist or doctor: they know which form suits your age, your sex, your other medicines and the state of your scalp. To work out who to see, read which doctor to see about hair loss.

Side effects, in plain words

They’re the same for both forms, according to the foam’s label, which pools data from both⁴:

• reactions where you apply it: itching, redness, dryness, flaking, sometimes eczema, including on the ears or face;
• hair growing somewhere other than the scalp, including on the face in women;
• temporary shedding at the start of treatment;
• more rarely, dizziness, low blood pressure, a racing heart, chest pain, unexplained weight gain or swollen hands and feet. If that happens, stop and see a doctor.

Facial hair is more common at 5%. In one trial in women, 46% of those on the 5% solution reported it, against 22% on the 2% solution and 16% on placebo⁵. It usually comes from the product spreading: dermatologists advise applying it at least 2 hours before bed, so it doesn’t end up on your pillow⁵. Labels also report body hair growth in babies who touched treated skin: keep your child away from the areas where you’ve applied it⁴.

Judging from photos, whichever form you use

Whether you switch from solution to foam because it itches, or start straight away with one or the other, the question stays the same: is it working for you? The mirror won’t answer that. From one month to the next, the change is too slow to see, and lighting changes everything.

The most reliable way is a baseline photo before your first application, then the same photo every week: same room, same light, same distance, dry hair. Calvap helps you frame each zone in the same spot by overlaying your previous photo as a see-through guide. After 6 months, you compare each zone with your first session. And if you switch form along the way, the date of the switch stays on the timeline, next to your photos.