Can I do laser or IPL on a client with darker skin?

It depends entirely on your machine — not on the client. This is different from treating a tan. A tan fades; Fitzpatrick V–VI skin is the client's baseline, and telling them to come back in two weeks is not an answer.

The physics: laser and IPL target melanin. Deeply pigmented skin has more of it everywhere, so a device that can't discriminate will deposit energy in the epidermis instead of the follicle. That means burns, blistering, post-inflammatory hyperpigmentation, or permanent hypopigmentation — and a higher keloid risk in clients already prone to it.

What is and isn't appropriate:

• Nd:YAG (1064nm) is the accepted choice for Fitzpatrick V–VI. The longer wavelength penetrates deeper and is absorbed far less by epidermal melanin.
• Alexandrite (755nm) and diode (810nm) carry meaningfully higher risk on skin above Fitzpatrick IV. Check what your manufacturer actually validates — not what a rep said.
• Broadband IPL is generally unsuitable for Fitzpatrick V–VI. It scatters across wavelengths melanin absorbs strongly. If your only device is IPL, the safe answer is referral.
• Patch test and wait longer. Post-inflammatory hyperpigmentation can take one to two weeks to appear, so a 48-hour check can pass and still miss it.

The bit people get wrong: refusing a client outright. Race is a protected characteristic under the Equality Act 2010, and "we don't treat dark skin" is a phrase you do not want read back to you. The defensible position is a documented equipment limitation plus a referral — "my device is validated to Fitzpatrick IV, so I'd be putting you at risk; here's a clinic with an Nd:YAG."

Record the client's Fitzpatrick type, the device and settings used, and the patch test date. That record is health-related data under UK GDPR, so it belongs somewhere secure and retrievable — not a paper diary.