The best body groomers for underarms

What makes an underarm different from the rest of the body

Every other area you groom is a surface. The underarm is a hollow, and three things follow from that which change what you should buy.

1. It only opens when the arm is up. With the arm down the skin folds into itself; with the arm up and behind the head it goes taut. That means the whole job is done one-handed, on the opposite side, in a mirror, with the working arm at an angle. A tool that needs two hands or a careful eye line is the wrong tool.
2. The hair grows in several directions at once. There is no grain here the way there is on a forearm or a chest. Anything that depends on going with the grain will miss, which is the argument for a comb and a slow pass rather than a close blade and a confident one.
3. You apply a regulated drug to it every day. This is the one that decides the purchase. Antiperspirant actives are drug-facts ingredients at published concentrations, and the strongest of them - 12 per cent aluminum chloride - comes with published directions to use it on completely dry skin at bedtime. Freshly shaved skin is not the skin those directions were written for.

The five, and what each one publishes

The pick: the tool that cannot go bare

The OneBlade 360 wins a category it was not designed for, on the strength of a limitation Philips publishes rather than hides: with a comb fitted it leaves between 0.2 and 5 mm across five settings, and without one it edges but still does not take hair off at the skin line. On a face that is a compromise. Under an arm, where the next thing to touch that skin is an acidic aluminum salt, it is the whole point.

Two more published figures carry it. It is 100% waterproof, so it can be used in the shower on hair that has had three minutes of warm water on it - which is a bigger difference on coarse underarm hair than any motor specification. And the blade carries a published 4-month life with a wear indicator on the blade itself, so the one maintenance decision in owning it is made for you. Nothing else here publishes a blade interval at all.

What you give up is runtime at 45 published minutes, which on this job is roughly twenty sessions, and a proprietary blade you will buy three times a year. The deeper argument for the same tool on reactive skin is on the sensitive-skin page, which ranks the whole category on the same axis: the shortest length it will leave.

If you want it bare anyway

Then the tool to buy is the Body Groomer 5000, and the reason is pricing rather than performance. Philips publishes the same dual-head architecture on it as on the Series 7000 - a trim side and a shave side, so there is no head to swap mid-job - the same count of 11 length settings, the same Triple Protect shave system of pearl tips, diamond-shaped holes and a guard, and the same 2-year warranty with a registration window. It sits at roughly half the 7000's money.

Two honest gaps. Philips does not publish a runtime on its own product page for this model - the 100-minute figure appears on the retail listing, which is Philips' copy but not Philips' spec sheet, and we are not going to print it as though it were. And the 11 settings are published as a count and never as a millimeter range, which is the figure this entire page turns on. You are buying a shave side you can verify and a trim side you cannot measure.

• Do it at night, not in the morning. If you go bare and then use a clinical-strength antiperspirant, you are applying a published 12 per cent aluminum chloride to skin you have just abraded. Leave a day between the two.
• Switch the deodorant, not the blade. If a bare underarm itches all day, a five-ingredient aluminum-free gel removes four variables at once - the sensitive deodorant page ranks those on published lists.

If you want to choose the length yourself

The Lawn Mower 3.0 Plus is the one to buy, and it is the best-disclosed tool on this page by some distance: a published 600 mAh cell and up to 60 minutes, two adjustable combs across a published 2 to 12 mm, IPX7 - a real immersion standard rather than a marketing adjective - and a published 2-year warranty. For underarms the useful end of that range is the top of it, not the bottom.

The 5.0 Ultra adds a 1.4 mm fixed comb and a second, foil head, and matches the 3.0 Plus on every other published figure. If the foil finish is what you want, that is a legitimate 40-dollar upgrade; if it is not, you are buying a travel case and a battery meter.

The order that causes the fewest problems

1. Shower first. Three minutes of warm water is the cheapest performance upgrade available to any of these tools, and it is the reason a waterproof rating matters more than a motor figure here.
2. Arm up and behind the head. This is what turns a fold into a flat surface. Do the whole side in that position rather than putting the arm down to check.
3. Longest comb, several directions. There is no grain, so work across the area twice at an angle to the first pass rather than once hard in one direction.
4. Rinse the tool, not the skin. Soap and water on the blade afterwards; nothing with alcohol or fragrance on the skin. The full technique for the rest of the body is on the body hair guide.
5. Antiperspirant the next night. Dry skin, bedtime, and a day's gap if you went close.

What not to use

• A back shaver. The baKblade tools publish a three-inch rigid swath on an 18-inch handle, which is exactly right for a back and unusable in a hollow the size of a palm. They also shave to the skin, which is the thing this page is arguing against - the back shaver page is where they belong.
• A depilatory cream. Thioglycolate creams carry published time limits and required patch tests, and the underarm is thin, warm, occluded skin - the cream page covers the published warnings, including the one product whose own instructions contradict each other.
• Your face trimmer. Covered in the FAQ above, and the reason is hygiene rather than capability.
• A cartridge razor, in the morning. If you are going to use a blade, the problem is not the blade, it is the hour. See the skip note and the antiperspirant directions above.