In order to understand if sunscreen prevents tanning, it’s important to know the three mechanisms by which skin gets tanned.
IPD – Immediate Pigment Darkening is a transient phenomenon that occurs within minutes of UV exposure. It initially appears as a greyish colour before fading to a brown colour over a day or so. It is thought to be mainly a result of melanin oxidation and doesn’t appear to have any protective effect from UV radiation. It is particularly activated by UVA rays.
PPD – Persistent Pigment Darkening is a longer phase of tanning that appears brown in colour, lasting 3-5 days. PPD is also thought to be caused by melanin oxidization and is more strongly activated by UVA than UVB.
DPD – Delayed Pigment Darkening is caused by either UVA or UVB rays. It appears 2-3 days after sun exposure and usually lasts for a month or so before starting to fade. It may take several months for the skin to return to its base constitutive colour. It is caused by the increased activity of melanocytes resulting in an increase in melanin production and transfer. This type of tanning does seem to have some UV-protective effect.
Using a broad-spectrum sunscreen when exposed to sunlight can delay or prevent tanning depending upon the actual duration of sun exposure.
Wondering whether dark skin still experiences tanning? Read our blogs on how dark skin tans and the need for sunscreen for dark skin tones
to know more