The most common method used to evaluate the UVA protective level of a sunscreen product is the Critical Wavelength test. Learn more about sun protection testing terms below:
- Critical Wavelength is a laboratory test method using specially formulated tape that measures UV transmission with and without sunscreen. In this method, the absorption spectrum of the sunscreen is measured against wavelength. The wavelength where 90 percent of absorption occurs is defined as the critical wavelength. The more potent the UVA protection, the longer the critical wavelength.
- Photostability is the ability (especially of a sunscreen ingredient) to retain potency and effectiveness for some hours after exposure to ultraviolet radiation (UVR) from the sun or tanning machines.
- Contact Irritancy is done to see if the product would cause irritation or an allergic reaction.
- Phototoxicity is a harmful skin reaction that occurs when using a photosensitizing product (product such as medicines or cosmetics that render skin excessively vulnerable to ultraviolet light), followed by exposure to ultraviolet light. Typically, within minutes or hours after UV exposure, the initial reaction or change in the skin appears, resembling a severe sunburn, often accompanied or followed by reactions such as blistering or itching.