Rosemary & Onion Growth Shampoo

Caffeine is the most studied of the four, and the one study that genuinely applies to a shampoo measures where the caffeine goes, and says nothing about whether hair grows. Using laser scanning microscopy, researchers showed that caffeine from a shampoo massaged in for two minutes and then rinsed off does reach the hair follicle, and stays detectable there for around a day. That tells you it gets in, which is a different claim from saying it grows hair. The trial that gets quoted in caffeine's favour was open label, funded by a caffeine shampoo manufacturer, measured an anagen ratio off a trichogram instead of counting hairs, and tested a leave-on liquid applied twice a day. It is weak evidence, and none of it carries across to a wash.

Rosemary extract rests on one small human trial from 2015, which has been carried a great deal further than it can bear. It was small, only loosely blinded, has not been repeated, and it ran on a leave-on rosemary oil used daily for six months. That is a different product in a different format from an extract you rinse out two minutes later. The evidence for rosemary is thin next to what exists for minoxidil, and whatever there is of it belongs to the oil. Rosemary is here because it is pleasant on the scalp and because it is the ingredient people come looking for.

Onion bulb extract traces back to a small 2002 study in which crude onion juice was applied to patches of alopecia areata, which is an autoimmune condition and a different problem from pattern thinning. It was raw juice rather than a cosmetic extract, and it has not been replicated in men with androgenetic hair loss. Onion is genuinely rich in quercetin and in sulphur compounds, and the honest position is that nobody has shown this does anything for thinning hair.

Panthenol, or pro-vitamin B5, is the ingredient doing the most reliable work here, and what it does is cosmetic. It holds water and deposits along the hair shaft, which reduces friction when you comb, makes hair easier to handle and leaves it looking a little fuller. That is an effect on feel and appearance, and it is true at that level.

The base is built on milder surfactants and a moderate sulfate load, well short of a stripping one. A scalp already being degreased daily by an alcohol-based topical does not need more of the same. The bottle holds 300 mL, which is roughly sixty washes.

This is the wash for men who are thinning and want the routine to include something they were going to do anyway. It does not compete with treatment, and it is not a treatment itself. If you are treating pattern loss, the Minoxidil Topical Solution is the product in this range with real regrowth evidence behind it, and this shampoo is what you wash with in between. If the rosemary and caffeine stories are what drew you here, the formats where those ingredients were actually studied are leave-on ones, so the Rosemary Hair Oil and the Caffeine Scalp Serum are the honest answer rather than a second bottle of shampoo. Pair it at the same wash with the Caffeine Conditioner if your lengths need the help. If your actual complaint is flaking rather than thinning, the Anti-Dandruff Shampoo is the better shampoo to be using, and you can come back to this one once the scalp has settled.

Three or four times a week, or daily if that is already your habit.

1. Wet your hair and scalp thoroughly with comfortably warm water.
2. Dispense roughly a 10p-sized amount, about 5 mL, and rub it between wet palms so it is already loose before it touches your head.
3. Work it into the scalp with your fingertips for about a minute, using the pads and not your nails. Your scalp is what you are washing, and the lengths get whatever runs through them.
4. Leave it on for two full minutes before you rinse. This is the step almost everyone skips, and it is the only reason the caffeine has any chance of reaching a follicle.
5. Rinse thoroughly until the water runs clear, then finish with a cooler rinse.
6. If you are conditioning, apply it through the mid-lengths and ends and keep it off the scalp.

Order matters. If you use topical minoxidil, wash first and apply it to a dry scalp afterwards. Applying minoxidil and then washing within four hours throws that dose away, and no shampoo is worth a lost dose.

What this product does is cosmetic and it happens quickly. A scalp that feels cleaner and less tight, and hair with a bit more body to it, are things you should notice within a wash or two. If it suits you, you will know inside a fortnight.

Your hair density will not change because of a shampoo. Contact time is measured in minutes and the formula is designed to be rinsed away, so judge this bottle on whether your scalp is comfortable and your hair behaves. Judge regrowth on whatever leave-on treatment you are using, and give that six months before you decide.

For external use only. Keep it out of your eyes, and rinse with plenty of water if it gets in. Onion and rosemary are botanical extracts, and botanicals are among the more common causes of contact allergy, so if your skin reacts easily, patch test a small amount behind the ear and wait twenty-four hours before you wash with it.

Do not use it on a scalp that is broken, inflamed, infected or sunburnt. Stop using it if you develop redness, itching, burning or a rash, and see a doctor if that does not settle. Keep it out of reach of children.

This is a cosmetic product. It does not treat, cure or prevent hair loss, and sudden, patchy or unexplained hair loss is a reason to see a doctor rather than to change shampoo.