UVB

UVB — a type of ultraviolet radiation with shorter wavelengths that mainly affects the surface layers of the skin and is the primary cause of sunburn. Its intensity varies with time of day, season, and altitude, and it plays a key role in the development of many skin cancers.

Key points

• UVB rays have shorter wavelengths than UVA and act mainly on the outer epidermal layers of the skin.
• UVB is the primary cause of sunburn and is a major factor in the development of many skin cancers.
• UVB intensity is strongest around midday, in summer, at high altitudes, and near reflective surfaces like snow and water.
• SPF ratings primarily reflect the level of protection a sunscreen provides against UVB radiation.

Frequently asked

Does UVB cause sunburn?

Yes, UVB is the main cause of sunburn and is also the primary type of UV that the SPF value on sunscreen measures protection against.

Is UVB blocked by window glass?

Standard window glass blocks most UVB, but this does not eliminate UV risk indoors because UVA can still pass through, so broad-spectrum protection is helpful.

Related topics

• What Is a Humectant?
• What Is the Skin Barrier?
• How UVA and UVB Differ

This is a foundational entry in the SYNC Skin Encyclopedia and is expanded over time. Educational information only — not medical advice.