Laser hair removal: what to do before and after

Laser hair removal works because the machine is aiming at one specific target: the pigment in the hair inside the follicle. Energy travels down the shaft, reaches the root and heats it until it's disabled.

Everything below follows from that. Remove the root and there's no target. Tan the skin and it competes for the energy. Leave the hair long and it burns above the surface instead of below it.

The four weeks before

No waxing, tweezing or bleaching. For at least four weeks. All of those remove hair from the root, which is exactly what the laser needs to find. If you turn up freshly waxed, the session does nothing — even though it feels the same.

Stay out of the sun and off the sunbed. Two to four weeks beforehand, on the area being treated. Tanned skin has more melanin at the surface, absorbs part of the energy, and raises the risk of burns and pigmentation. If you've just come back from the coast, tell us and we'll reschedule. That's not bureaucracy, it's safety.

Tell us about your medications. Several increase photosensitivity: isotretinoin, some antibiotics such as tetracyclines, certain diuretics and anti-inflammatories, and supplements like St John's wort. Isotretinoin usually requires waiting several months after finishing the course. Also mention if you're prone to cold sores, if you use retinoids or acids, or if you're pregnant or breastfeeding.

On the day

Shave the area twelve to twenty-four hours beforehand. With a razor, close to the skin. This doesn't contradict the above: shaving cuts the hair but leaves the root intact. Long hair scatters the energy at the surface, which hurts more and treats less.

Arrive with clean skin. No creams, oils, deodorant, make-up or self-tanner. Any layer gets in the way.

No fake tan for the two weeks before, even if you haven't been in the sun. The machine reads that pigment as though it were a real tan.

What it feels like

Like an elastic band snapping against the skin, fast and repeated, with a sensation of heat. Thin-skinned areas — bikini, upper lip, underarm — feel it more. An underarm takes ten minutes; full legs, forty.

Afterwards it's normal to see redness and slightly raised follicles, like goosebumps. That settles within hours and is actually a good sign: it means the energy reached where it needed to.

The days after

• Cool the area for the first few hours if it stings. A cool compress, not ice directly on the skin.
• SPF 50 every day on the treated area for the length of the course. This is the single biggest thing that prevents pigmentation.
• No heat for the first forty-eight hours: no sauna, jacuzzi, steam, very hot water or hard exercise.
• Loose cotton clothing on day one, especially for groin and underarms.
• No scrubs, retinoids or acids on the area for three or four days.
• Don't pull out the hair that appears. Between seven and fourteen days you'll see hair emerging — it isn't growing, it's being shed. Let it fall out or shave.

How many sessions

The laser only disables follicles that are in their growth phase, and at any given moment only a portion of your hair is. That's why it has to be repeated, and why the interval matters: every four weeks on the face, every eight on the body. Moving an appointment earlier doesn't speed anything up, it just wastes a session.

Most people need somewhere between six and ten sessions for a significant reduction, then occasional top-ups. The number varies with hair thickness, the area, skin tone and hormonal factors; polycystic ovary syndrome or thyroid conditions usually mean more.

Worth saying plainly: blonde, white, grey and red hair contain almost none of the pigment the machine needs, and respond poorly or not at all. If anyone guarantees you results on white hair, be sceptical.

Why the consultation matters

At the consultation — which is free — we look at your skin phototype, hair type, medical history and medications, and set the machine's parameters from that. The same setting that's safe on fair skin can burn darker skin.

It's the least glamorous part of the process and the one that most determines the outcome. It takes fifteen minutes.