You’re probably thinking: the stronger the better, right? When it comes to minoxidil spray, that’s not necessarily the case. Evidence suggests that solutions with 5% of the active ingredient, minoxidil, works best of all for stopping hair loss and boosting regrowth.
What is minoxidil?
Originally used as a treatment for high blood pressure, doctors noticed patients were experiencing an unexpected side effect: they were growing extra hair. This led to the development of a topical formulation of minoxidil (aka, a spray) specifically for treating androgenetic alopecia (male pattern baldness) in the late 1980s.
How minoxidil works to stop hair loss and promote growth isn’t fully understood yet, it is thought to:
- extend the anagen (growth) phase and shorten the telogen (resting) phase, promoting the growth of longer, thicker hair
- increases blood flow to the hair follicles, bringing vital oxygen and nutrients needed for proper functioning of the hair growth cycle
- promoting the expression of growth factors.
These different pathways effectively counteract the detrimental effects of the hormone dihydrotestosterone (DHT) on sensitive hair follicles, with around 84% of patients seeing their hair loss stop or even reverse within 3-6 months of using the treatment.
Are higher strengths better?
To make a long story short: no, we don’t think so. Even though it’s logical to assume that solutions containing higher dosages of minoxidil would work better for hair growth, trials seem to suggest it’s not the case.
A 2021 clinical trial comparing minoxidil 5% to minoxidil 10% found that participants using the 5% version actually saw better results. Plus, the group using the 10% spray experienced more side effects, like extra shedding, scalp irritation and hypertrichosis (unwanted hair growth).
Another trial in 2024 also compared the two concentrations, but this time, the group using the 10% spray did see slightly better regrowth at the front of the scalp, but the results across the rest of the scalp were basically the same. But once again, the 5% spray caused less side effects than the 10%.
The reason why higher strengths don’t seem to be more effective, and cause more side effects, comes down to how minoxidil is absorbed by the scalp. As the minoxidil molecule is too large to penetrate the skin by itself, it is usually dissolved in an alcohol called propylene glycol. The most common side effects caused by minoxidil spray, like scalp irritation and dryness, are actually caused by a sensitivity to propylene glycol, rather than by minoxidil itself.
But the maximum amount of minoxidil that can be absorbed by propylene glycol is about 7.5%. Anything above this concentration starts to crystallise and will not be absorbed by the scalp, which is why it is not more effective. Using higher concentrations of minoxidil means using more propylene glycol, which increases the risk of side effects.
What about 2% minoxidil?
When comparing 5% to 2%, the research is pretty clear: 5% just performs better.
A major study of 393 men found that the 5% formula produced 45% more hair regrowth after 48 weeks compared with the 2% version. On top of that, the men using 5% started seeing improvements sooner, a big plus when you’re trying to stay ahead of hair loss. Both strengths were generally well tolerated, though the 5% group did report slightly more itching and scalp irritation.
A separate study on women with female pattern hair loss showed nearly identical results: the 5% solution consistently outperformed 2% across all measures. In short, regardless of gender, the higher concentration tends to deliver stronger regrowth.
That said, 2% can be a good choice for people with very sensitive scalps, but it often works more slowly and might not deliver the same level of results. If irritation is the issue, switching to an alcohol‑free spray or trying Oral Minoxidil (the capsule version) is usually a better option than dropping down to 2%.
Why Sons use 5% minoxidil spray
5% is the concentration officially licensed by the MHRA for treating male pattern baldness, which Sons holds the license for this formulation, along with 1mg finasteride. It consistently hits the sweet spot between effectiveness and safety.
It can cause mild dryness or irritation for some users, but these effects usually settle once treatment is stopped or switched. For anyone who struggles with topical minoxidil, oral minoxidil can be a great alternative. It avoids local scalp irritation altogether, and many people find it easier to stay consistent — one pill a day versus twice‑daily application of a spray.
All of our blog articles are reviewed by our Medical Director before publication.
