Sunscreens and Sunblocks

Preparations containing chemicals that help to protect the skin from the damaging effects of the sun’s ultraviolet radiation

Common drugs

  • Aminobenzoic acid

  • Avobenzone

  • Bemotrizinol

  • Bisoctrizole

  • Dioxybenzone

  • Ethylhexyl methoxycinnamate

  • Methylbenzylidene camphor

  • Octinoxate

  • Octocrilene

  • Oxybenzone

  • Padimate-O

  • Para-aminobenzoic acid

  • Titanium dioxide

  • Zinc oxide

Sunscreens and sunblocks contain a variety of chemicals that help to protect the skin from the damaging effects of ultra-violet (UV) radiation present in sunlight. UV radiation is composed of UVA and UVB rays, both of which age the skin. In addition, UVA rays cause tanning, and UVB rays cause burning (see Sunburn). Excessive exposure to sunlight also increases the risk of skin cancer. The sun’s rays can cause cancerous changes to occur in the skin because they progressively damage the genes that control important functions in the skin, such as cell division.

Using sunscreens or sunblocks protects against these harmful effects and is advisable for anyone spending time in the sun. The use of these preparations is particularly important for people with fair skin and young children, whose skin is more vulnerable to sun damage (see Safety in the sun).

If your skin becomes sensitive to the sun (see Photosensitivity), you may need to use sunscreen or sunblock even when you are not exposed to strong sunlight. UV sensitivity may develop in people who are taking certain types of drug, such as some oral contraceptives (see Contraception), antibiotics, and thiazide diuretics (see Diuretic drugs).

How do they work?

Sunscreens protect the skin by absorbing UVB rays, thereby reducing the amount that enters the skin; sunblocks provide a physical barrier that reflects or scatters UVA and UVB rays. Substances in sunscreens that absorb UVB rays include para-aminobenzoic acid (PABA) and padimate-O. Sunblocks contain chemicals such as zinc oxide and titanium dioxide, which are opaque and therefore reflect and scatter both UVB and UVA rays. Sunscreens are graded using a sun protection factor (SPF), which is a measure of the level of protection they provide against UVB rays. The higher the rating, the greater the protection against this type of radiation. However, even sunscreens with a high SPF do not provide complete UVB protection.

How are they used?

Sunscreens and sunblocks are available as creams, lotions, gels, and sprays. All products need to be applied frequently and generously to maintain protection, especially after swimming. You may experience irritation or an allergic rash when using certain sun protection products, particularly those containing PABA.


Reapply sunscreens regularly, particularly after swimming or if you are sweating.

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

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