Underarm Laser Hair Removal: Sessions, Pain & Price

Underarm laser hair removal delivers light energy to the pigment in the hair roots beneath the arm, so that the roots are weakened and regrown hair comes in finer. The number of sessions differs from person to person: Mayo Clinic notes that roughly 4-8 sessions are generally needed, and the American Academy of Dermatology notes that sessions are usually spaced 4-6 weeks apart. Underarms with dense hair may need more sessions than that, and a doctor will assess you individually. This is long-term hair reduction, not permanent hair removal, and results vary by individual.

How underarm laser hair removal works

Underarm laser hair removal works on the principle of selective photothermolysis: light energy is selectively delivered to the melanin (pigment) in the hair shaft and hair root, disturbing the surrounding tissue as little as possible. When the pigment absorbs the light energy, that energy converts to heat and passes on to damage the cells that control hair production. The result is that regrown hair tends to be finer, lighter in colour, and slower to appear than before.

The wavelengths used in hair reduction sit in the range of roughly 600-1100 nm, because that is the range melanin absorbs well. Devices commonly found in clinics include Alexandrite 755 nm, where melanin absorbs energy strongly and which is often used on light to medium skin tones; Diode 810 nm, which penetrates deeper and can be used across many skin tones; and Nd:YAG 1064 nm, where the upper layers of skin absorb less energy, which is why it is often chosen for darker skin tones. Some newer devices combine several wavelengths in a single handpiece so the settings can be adapted to skin tone and hair thickness.

Because the laser responds to “the pigment in the hair shaft”, underarm hair that is thick, dark, and fully developed (terminal hair) tends to respond well, while light, fine, white, or grey hair responds less because it contains little pigment. On the other side, skin that is darker or has recently had strong sun exposure has more melanin in its upper layers; if the energy settings are not appropriate, heat can build up in the skin instead of reaching the hair root, raising the risk of redness, patchy dark marks, or burns. For that reason, assessing skin tone on the Fitzpatrick scale, the characteristics of the hair, and your skin care history before starting is a step that cannot be skipped. Read an overview of the technology on the laser hair removal page.

After each session, hair does not fall out immediately. Hair shafts that have been heated are gradually pushed out of the follicle over roughly 1-3 weeks. Some people see what looks like slight continued growth in the early days, which is the normal shedding process for the hair shaft — do not pick at it, pluck it, or pull it out with tweezers.

How many underarm laser hair removal sessions until the hair is gone

The short answer is that the number of sessions differs from person to person. Mayo Clinic notes that roughly 4-8 sessions are generally needed, and the American Academy of Dermatology notes that sessions are usually spaced 4-6 weeks apart. Underarms with dense hair may need more sessions than that, and a doctor will assess you individually. Even after a full course you will still need periodic maintenance, because laser reduces the amount of hair — it is not permanent in the sense that hair will never grow again.

The reason multiple sessions are needed lies in the “hair growth cycle”, which is divided into three main phases: the growth phase (anagen), when the hair shaft is still connected to the hair-producing cells and pigment is at its densest; the regression phase (catagen), when the root begins to shrink; and the resting phase (telogen), when the hair shaft is shed and the follicle pauses temporarily. Laser responds clearly better to hair in the anagen phase than in the other two, because that is the phase where pigment is directly linked to the target cells.

At any given time, not all underarm hair is in the same phase. A proportion is in the growth phase and ready to take up the energy, while the rest is resting and does not yet respond. A single session therefore only reduces part of the hair. The American Academy of Dermatology notes that a reduction of about 10-25% is commonly seen after the first session and that most people can repeat treatment every 4-6 weeks. Getting the spacing to match the new cycle of hair is the heart of the course: if sessions are too close together the new cycle of hair has not yet emerged to be caught, and if they are too far apart that cycle of hair may already have entered the resting phase.

Overall, how much hair is reduced after a full course varies widely between individuals, depending on hair colour, hair density, hormones, and how consistently you keep your appointments — so there is no single number that applies to everyone. A small study of 40 women with Fitzpatrick II-III skin, using an Alexandrite 755 nm laser on the underarms for 3 sessions spaced 4 weeks apart, reported a reduction in hair count of about 91-94% when measured 1 month after the final session, with results maintained at the 6- and 12-month follow-ups. However, this was a small sample of 40 people, limited to Fitzpatrick II-III skin, and every participant had clearly dark hair, so it cannot represent the results of the general population. Individual results can differ considerably according to hair colour, density, hormones, and how consistently you keep your appointments. People with hormonal conditions, such as polycystic ovary syndrome, may see more regrowth and need continued care for longer.

Does underarm laser hair removal make the underarm whiter

To answer directly: laser hair reduction is not a direct treatment for dark underarm pigmentation and you should not expect your underarm skin colour to change. But many people feel their underarms “look brighter”, and there is an understandable explanation for that.

What makes underarms look dark comes in several overlapping layers. One is the dark stubble still sitting beneath the skin, which from the outside looks like grey dots across the area, making it read as a dull grey even when the actual skin colour has not become darker. When the amount of hair drops and there is less stubble under the skin, some people feel the overall look is smoother — but this is about how visible the stubble is, this is not a change in skin colour, and it differs from person to person. Another layer is repeated irritation from frequent shaving, waxing, plucking, and friction from clothing. This low-grade chronic inflammation triggers post-inflammatory hyperpigmentation, so when the need to shave or wax drops, the chance of new marks forming drops with it. A further layer is ingrown hair, or hair curled beneath the skin, which often leaves dark spots behind after it heals and tends to become less common as hair is reduced.

What laser hair reduction does not address is darkening caused by pigment in the skin itself — for example dark tones from genetics, marks from irritating deodorant products, marks from the friction of body weight and clothing, or thickened dark patches (acanthosis nigricans) linked to insulin resistance. This group needs a different approach, such as adjusting habits that cause skin friction, using topical medication prescribed by a doctor, or treatment with a laser designed for pigment. For example, the clinic’s Pico Laser Tone Up / Pigmentation programme is THB 2,000 per session, which is a treatment separate from a hair reduction course. The most suitable path is to have a doctor assess which cause is mainly behind your discolouration, then plan the order of care accordingly.

Does it hurt, and how does it feel during treatment

The most common sensation is like a light rubber band snapping against the skin, with a brief flash of heat in time with each pulse. For most people the intensity is mild to moderate, and because the underarm is a small area it usually takes only a few minutes per side.

Factors that make the sensation differ between individuals include hair density (the thicker and darker the hair, the more energy it absorbs, and the more noticeable the sensation), the energy setting used, the laser system, and each person’s skin sensitivity. The first session usually feels the most intense, and it often eases in later sessions as the amount of hair drops. The underarm study cited above reported that about 65-70% of participants felt mild to moderate pain and about 20-25% had temporary redness, which in that study faded within a few minutes of treatment.

Most clinic laser devices have a cooling system that helps reduce discomfort and protect the upper layers of skin — for example a handpiece with a chilled tip, cold air blown during the pulse, or a cooling gel applied beforehand. Some devices use a continuous gliding technique with lower energy per pulse instead of firing point by point, which many people find easier to tolerate. If your skin is very sensitive, a doctor may consider a topical anaesthetic about 30-60 minutes before treatment, or step the energy settings up gradually during the first session.

What you should tell your practitioner immediately is any stinging heat that “lingers” after the pulse has passed, or unusually sharp pain, because these are signs that the energy setting should be adjusted or the cooling increased. Do not endure it to the end on the assumption that more pain means better results. Settings that are too strong do not mean hair will be reduced faster; they increase the risk of redness, blistering, and patchy dark marks afterwards. After the session you may have red swelling like a mild sunburn and small raised red bumps around the follicles for the first few hours. A cold compress helps you feel more comfortable.

What to prepare before, and how to care for skin after

The simple principle is that before treatment you need “a hair root for the laser to target, but no hair on the skin surface”, and after treatment you need to reduce heat, friction, and irritants while the skin is still sensitive.

Preparation before your appointment

1. Avoid waxing, plucking, ripping hair out, or using an electric epilator for at least 2-4 weeks before treatment, because these methods pull the root out, leaving no target for the energy to work on.
2. Shave the underarm smooth 1-3 days before your appointment, using a sharp blade and a gentle shaving cream. Avoid shaving against the grain to the point of grazing the skin.
3. Stop using hair removal creams for at least 1 week, because the chemicals may make the skin more sensitive.
4. Avoid anything that darkens the skin before treatment — strong sun, tanning beds, and self-tanning products — for at least 2-4 weeks.
5. Disclose every medication and supplement you use, especially photosensitising medication such as isotretinoin, tetracycline/doxycycline antibiotics, or certain herbal products, and mention any history of cold sores or keloids.
6. On the day of treatment, come with no deodorant, powder, perfume, or moisturiser on the underarm.

Aftercare steps

1. A cold compress on the treated area is fine on the first day if it feels hot or looks red and swollen. Do not hold ice directly against the skin.
2. Avoid deodorant and antiperspirant for about 24 hours; cleanse with water and a mild soap instead.
3. Avoid heat buildup for the first 24-48 hours — saunas, hot tubs, steam rooms, and heavy exercise that makes you sweat a lot — because sweat and friction increase the chance of inflamed bumps around the follicles.
4. Choose loose, breathable clothing for the first 2-3 days to reduce friction under the arm.
5. Avoid exfoliating, scrubs, and products containing fruit acids or retinoids on the treated area for about 3-5 days.
6. Keep the skin hydrated with a gentle moisturiser. If the area may be exposed to sun — for example when wearing a sleeveless top — also apply sunscreen of SPF 30 or higher.
7. During the course, if hair grows and you want to manage it, you can shave as usual, but do not wax or pluck, and keep to the appointment timing your doctor sets.
8. If you have blistering, an open wound, ring-shaped skin colour changes, or increasing pain and redness after 2-3 days, contact the clinic so a doctor can assess it.

Who is not suitable, or should postpone treatment

Laser hair reduction is a procedure most people can have, but some situations call for postponing or for a doctor to assess case by case.

• Pregnancy or breastfeeding, because safety data is still limited, so most doctors advise waiting.
• The skin in the treatment area is inflamed — for example a rash, an open wound, an infected bump, or an active cold sore outbreak.
• Skin that has recently had strong sun exposure or tanning in the past 2-4 weeks, because the risk of patchy dark marks is higher.
• Currently taking isotretinoin, or having stopped it recently — doctors usually require an interval after stopping the medication before starting.
• Taking photosensitising medication such as certain antibiotics, certain diuretics, or certain herbal products; disclose everything so the plan can be adjusted.
• Tattoos or raised moles in the area to be treated must be avoided during the pulses, because their pigment absorbs energy very strongly.
• A history of keloids, raised scars, vitiligo, or skin conditions that can be triggered by injury to the skin.
• Conditions that cause abnormal hair growth, such as hormonal disorders, where the underlying cause should be investigated too — laser can reduce the hair that is there, but it does not correct the cause that makes new hair grow.

Side effects worth knowing about in advance include mild redness and swelling around the follicles, which usually settles on its own within 1-3 days; itchy red bumps from inflammation of the follicles (folliculitis), which is more common when sweat builds up and there is friction after treatment; temporarily darker or lighter skin, especially in darker skin tones or in people who do not avoid the sun; and, less commonly, blistering, scarring, or skin colour changes that last a long time. Another condition people often ask about is hair growing thicker than before in neighbouring areas (paradoxical hypertrichosis), which a pooled review of studies found in about 3% of people treated, mostly on the face or neck, and very rarely in other areas such as the underarms. In addition, the underarm study cited above reported increased underarm sweating after treatment in about 30-60% of participants depending on the group studied; some cases returned to normal on their own, while some persisted for as long as 12 months. This is worth discussing with your doctor if sweating is already a concern for you. Having treatment at a medical facility where a doctor assesses you and controls the energy settings helps reduce the chance of these side effects.

What does it cost, and is it better value than waxing

At Onnyx Clinic, underarm hair removal is THB 599 per session. Other areas people often combine with it are the beard at THB 599 per session, arms at THB 799 per session, back at THB 799 per session, full legs at THB 899 per session, face including beard at THB 999 per session, abdomen at THB 499 per session, and the bikini area at THB 1,299 per session.

Comparing costs should be done over the long term, not per session, because shaving and waxing are recurring costs at high frequency for life, while a laser course is one block of cost over 6-12 months followed by periodic maintenance. The table below summarises the differences between the methods.

In practice, some people who shave their underarms often or wax regularly report that the daily upkeep is lighter after a course. That said, the value depends on how often each person does it and the price they actually pay, so have a doctor assess you before deciding — and understand from the start that this is long-term hair reduction, not permanent hair removal, so periodic maintenance is still required. People with very light or very fine hair may see less effect and should have a doctor assess whether it is worthwhile before deciding. The prices shown are per session by area, while the number of sessions suited to you depends on hair density, skin tone, and your goals. Ask for more details via LINE.

References

• American Academy of Dermatology — Laser hair removal: FAQs
• Mayo Clinic — Laser hair removal
• DermNet — Laser therapy in skin of colour
• DermNet — Nd:YAG laser treatment
• JMIR Dermatology (PMC) — Long-Term Efficacy and Safety of 755-nm Alexandrite Laser for Axillary Hair Removal
• PubMed — Paradoxical Hypertrichosis Associated with Laser and Light Therapy for Hair Removal: A Systematic Review and Meta-analysis

Consult the Onnyx Clinic medical team

If you are considering underarm laser hair removal and want to know which laser system, what energy setting, and how many sessions would suit your skin tone and hair type, the medical team at Onnyx Clinic is glad to assess you and plan care individually — including a separate approach for underarm discolouration if it is found to come from another cause. Ask questions and book a consultation via LINE: @onnyxclinic

This content is for general information only and is not a diagnosis or individual medical advice. Results vary by individual. Please consult a doctor for an assessment suited to you.