Topical and Adjunct Anaesthetics
Status: draft compiled 2026-04-20.
Laser hair removal pain is typically mild to moderate per pulse and manageable with cooling alone for most body regions and Fitzpatrick levels. Some combinations — Nd:YAG on Fitz V-VI, bikini/Brazilian, perianal, chest in men, large-area leg or back, and trans genital pre-op clearance — reliably exceed patient tolerance without pharmacological support. This chapter covers the topical anaesthetic options, the nerve-block options, the oral analgesic options, and the systemic-toxicity ceiling that limits how much topical can safely be used over a large area.
Topical anaesthetic options
| Agent | Composition | Onset | OTC/Rx | Key risks |
|---|---|---|---|---|
| EMLA | lidocaine 2.5% + prilocaine 2.5% | 45-60 min under occlusion | OTC US | methaemoglobinaemia (prilocaine → o-toluidine); infants/G6PD/MetHb reductase deficiency; lidocaine systemic toxicity on large/broken skin |
| LMX-4/5 | liposomal lidocaine 4%/5% | 30 min, no occlusion | OTC | prilocaine-free, so lower methaemoglobinaemia risk; still CNS/CV if abused |
| Ametop | tetracaine 4% gel | 30-45 min | Rx/OTC UK | higher local erythema than EMLA |
| BLT (compounded) | benzocaine 20% + lidocaine 6% + tetracaine 4% | 30-60 min | Rx compounded | benzocaine methaemoglobinaemia (FDA box warning 2018); corneal injury if near eye |
| Pliaglis | lidocaine 7% + tetracaine 7% peel | 20-30 min | Rx FDA-approved | erythema 47%, discolouration 16%, edema 14% |
Sources: EMLA product information; LMX-4 OTC label; Pliaglis FDA label 2013; Amethocaine review, PMID 15777110. Confidence: C2.
EMLA is the default OTC topical in US practice. It requires occlusion (plastic film cover) for 45-60 minutes before achieving peak effect. The prilocaine component carries a theoretical methaemoglobinaemia risk — o-toluidine, a prilocaine metabolite, oxidises haemoglobin — but this is a practical concern only in infants, G6PD-deficient patients, and patients with methaemoglobin-reductase deficiency. A 2019 case report of methaemoglobinaemia after laser hair removal with EMLA appeared in the literature (PMID 31477356).
LMX-4 or LMX-5 is prilocaine-free liposomal lidocaine, reaching effective anaesthesia in ~30 minutes without occlusion. It is a reasonable substitute for EMLA in patients who cannot tolerate prilocaine, in pediatric or infant cases, or when convenience matters.
BLT (compounded benzocaine-lidocaine-tetracaine) produces deeper anaesthesia than single-agent creams and is often requested for bikini, Brazilian, or male-chest sessions. It must be compounded by a licensed pharmacy at reasonable concentrations; high-concentration ad hoc compounding is the class of product associated with fatal systemic toxicity (see below).
Pliaglis is the FDA-approved self-occluding peel containing lidocaine 7% plus tetracaine 7%. It is applied as a cream, dries to a thin film in 20-30 minutes, and is peeled off before the session. Short onset and high effectiveness make it popular for laser hair removal on large areas.
The lidocaine systemic-toxicity ceiling
Lidocaine has well-characterised systemic toxicity at elevated plasma concentrations: CNS effects (tinnitus, tingling, seizures) at 5-10 μg/ml; cardiovascular effects (hypotension, arrhythmias, cardiac arrest) at 10-25 μg/ml; death above those ranges. The dose cap for topical application in adults is conventionally ≤ 4.5 mg/kg plain lidocaine or ≤ 7 mg/kg with epinephrine. Absorption from intact skin is relatively modest at standard concentrations; absorption from large-area topical application under occlusion, from compounded high-concentration creams, and from broken or abraded skin is much higher.
Two fatal cases frame the clinical importance of this cap:
- 2004, Kristie Rae Kubicek, 22, cardiac arrest driving to a laser appointment after applying a home-compounded 10% lidocaine cream under occlusion to her legs and torso.
- 2005, Shiri Berg, 22, NC, death after a clinic-supplied compounded lidocaine + tetracaine cream was applied under occlusion to her legs in preparation for a laser hair removal session. Found seizing in her car; she died the following day. Compounding pharmacy and clinic sued.
Both cases resulted in FDA action. The FDA 2007 Public Health Advisory specifically targeted compounded high-concentration topical anaesthetics applied under occlusion for laser hair removal. Industry practice shifted toward lower-concentration standardised products and explicit dose-area caps.
Practical rule of thumb: a 70 kg adult can tolerate roughly 300-500 mg lidocaine topically at standard concentrations. A 60 g tube of 4% LMX-4 contains ~2,400 mg lidocaine; fully absorbed, this exceeds the systemic toxicity range. Real-world absorption from intact skin rarely approaches 100%, but the margin narrows dangerously with compounded high-concentration creams, with large treatment areas, with broken or abraded skin, and with occlusion. Most clinics cap topical anaesthetic application to ≤ 60 g tube per session for an average adult, restrict to one body region per session, and avoid compounded products above 10% lidocaine.
Sources: Dermatology Times lidocaine toxicity coverage; FDA 2007 advisory. Confidence: C1.
Nerve blocks
Local injected anaesthetics (lidocaine 1-2% ± epinephrine, bupivacaine 0.25-0.5%) can be delivered at specific nerve foramina to produce regional anaesthesia that lasts 1-3 hours without the surface-area limitations of topical creams. Standard blocks in hair-removal practice:
- Infraorbital block: for upper lip, lateral nose, and lower lid / upper cheek. 1-2 ml lidocaine 1-2% through the infraorbital foramen. Onset <5 minutes, duration 1-2 hours.
- Mental block: for chin and lower lip. 1-2 ml through the mental foramen.
- Supraorbital and supratrochlear blocks: for forehead (rarely needed for hair removal).
- Spermatic cord / scrotal block: for pre-vaginoplasty scrotal electrolysis or laser. Lidocaine or bupivacaine at the spermatic cord with epinephrine to extend duration. 3-8 hours of dense anaesthesia; the standard for multi-hour trans pre-op scrotal sessions.
- Pudendal block: for perianal and perineal work. Lidocaine or bupivacaine at the pudendal nerve in the ischiorectal fossa, typically requiring ultrasound guidance or specific anatomical landmarks.
Nerve blocks are performed by physicians or by specifically-trained nurse practitioners or physician assistants depending on state scope of practice. They are standard in high-volume trans-specialty practices and in hair-removal clinics that handle pre-operative surgical clearance; many community laser clinics do not offer them. Sources: Dermatologic Surgery nerve block reviews; standard anaesthesia textbooks. Confidence: C3.
Oral analgesics
Oral analgesics reduce perceived pain modestly without addressing the local nociceptor activation directly. Ibuprofen 400-800 mg 30-60 minutes before the session is the standard; acetaminophen 1000 mg is an alternative for patients with NSAID contraindications. Combined acetaminophen-ibuprofen at these doses is synergistic. Oral opioids are rarely appropriate for laser hair removal sessions; they are sometimes used for very long trans pre-op sessions with benzodiazepine sedation.
Benzodiazepines (lorazepam 0.5-1 mg or diazepam 5-10 mg 30-60 minutes before) reduce anticipatory anxiety and improve session tolerability for anxious patients. They do not reduce nociceptor firing at the treatment site but change the patient's experience of the pain. Prescribed occasionally, typically for first-session anxiety management. Confidence: C3.
Nitrous oxide
Some high-end clinics offer nitrous-oxide-oxygen inhalation during long or painful sessions. 50/50 nitrous/oxygen delivered through a nasal or oral mask provides rapid-onset, rapid-offset analgesia with minimal systemic side effects. Nitrous does not eliminate pain but reduces perceived pain and anxiety, making longer sessions more tolerable. Logistically expensive (gas supply, delivery equipment, practitioner certification in some jurisdictions) so mainly available at medical-spa or trans-specialty high-volume clinics. Evidence base: anaesthesia literature generally; hair-removal-specific RCTs thin. Confidence: C3.
Cost comparison
- EMLA 30 g tube: $15-40 OTC
- LMX-4 30 g tube: $25-50 OTC
- Pliaglis 30 g tube: $40-80 Rx
- BLT compounded 30 g: $50-100 Rx (varies by pharmacy)
- Nerve block (physician): $75-250 per block
- Oral ibuprofen: $0.05/dose
- Lorazepam prescribed: $10-30 for a 5-tab prescription
- Nitrous session: $75-200 extra per session
For most laser hair removal sessions, OTC topical plus oral ibuprofen is sufficient. Compounded or prescription topicals are reasonable for high-pain regions or for patients with low tolerance. Nerve blocks are standard for trans genital pre-op and rare in general practice. Confidence: C3.
What not to do
Do not apply ad hoc compounded high-concentration lidocaine creams (>10%) under occlusion to large areas. This is the failure mode that killed Kubicek and Berg; it remains the specific scenario the FDA advisory targeted.
Do not exceed package-sized topical doses on the assumption that "more is more"; systemic absorption rises steeply with dose and duration.
Do not apply topical anaesthetic to broken or abraded skin; absorption is dramatically higher.
Do not use benzocaine-containing creams (BLT) near the eye; corneal injury is documented.
Do not assume that pre-session topical anaesthetic eliminates all pain; it reduces peak pain but most patients still experience moderate discomfort during pulses in sensitive areas. Confidence: C2.