This refers to sunscreens that are formulated to contain ingredients that absorb both UVA and UVB rays. Products do not necessarily contain UVB and UVA absorbers unless they are specifically formulated for broad-spectrum protection.

Chemical sunscreens provide a protective layer of sunscreen ingredients that absorb ultraviolet radiation. When UV light is absorbed by the sunscreen, the most common reaction is for its energy in the form of sunlight to be converted to heat, which is then dissipated.

Also known as sunburn, erythema is a visible sign of skin damage, usually redness incurred by overexposure to the sun's ultraviolet rays. The amount of time a person can stay in the sun without protection before beginning to burn is known as the minimal erythema dose (MED)

The kind of exposure received unintentionally during everyday activities. For the average person, incidental time spent in the sun accounts for 80% of their lifetime exposure. For this reason, dermatologists emphasize the need to protect the skin with clothing or a SPF on a daily basis.

A sunscreen that is non-comedogenic will not clog the skin's pores. Many special protection products are designed for facial use and are non-comedogenic.

Dermatologists use this term when referring to sun induced skin damage. Photoaging is a process that starts at youth, although the more obvious skin changes, such as wrinkles, freckles, and leathery texture and loss of elasticity, may not become obvious for decades. Using a high SPF sunscreen (SPF 15 +) on a regular basis can protect the skin from further damage. There is evidence to suggest that the skin has the ability to heal itself, thereby reversing many signs of photoaging.

In certain situations, exposure to ultraviolet radiation can cause skin reactions, such as exaggerated sunburn. For example, people who are taking certain anti-biotic, tranquilizers, diuretics, and other drugs may experience photosensitivity. The skin reaction may consist of itching, inflammation, or a rash. Individuals who experience photosensitive reactions are often advised by their physicians to minimize exposure to sunlight and protect the skin with clothing and a high SPF sunscreen.

Physical sunscreens such as zinc oxide or titanium dioxide, prevent the sun's rays from penetrating the skin by blocking and reflecting the ultraviolet radiation rather than absorbing it.

The most common adverse reaction to the sun is the ordinary sunburn- also known as erythema. Burns from the sun are induced primarily by UVB radiation. The injury they cause is characterized by delayed redness and swelling followed by tanning and peeling. Sometimes, the skin darkens without reddening, but that does not mean that damage has not occurred. Chronic sun damage and sunburns in the first 18 years of life typically result in dry, wrinkled skin, irregular pigmentation and pre-cancerous changes.

The sun protection factor (SPF) is a ratio between the ultraviolet dose required to produce the start of a sunburn on protected skin (sunscreen) compared to unprotected skin (without sunscreen). The SPF number indicates how many times longer a person can stay in the sun before beginning to burn while wearing sun protection than if he/she were not wearing any sunscreen at all.

This formula bonds to the skin on contact, allowing sunscreens to deliver sweat-resistant protection without leaving a filmy residue. Sunscreens with this formula let fitness enthusiasts enjoy outdoor activities with the confidence that the sunscreen will not let their grip slip or run into their eyes causing stinging.

Water resistant - must maintain its degree of SPF protection for a minimum of 40 minutes in the water. Very water resistant - must maintain its degree of SPF protection for a minimum of 80 minutes in the water.