Slide show: How the sun damages your skin

You may walk away from the beach with a suntan, but that's not all you're getting. Excessive sun exposure is responsible for much of the skin damage associated with aging. This damage accumulates slowly over time and starts at an early age. Much of the skin damage is merely cosmetic, but some effects, such as skin cancer, are more serious.

Do you know how the sun damages your skin? See the results of ultraviolet radiation so you can recognize the signs of too much sun.

To protect itself from the damaging effects of the sun, your skin increases its production of melanocytes. These cells produce the dark brown pigment called melanin. The extra melanin makes your skin look darker or suntanned. In some cases, the sun causes an uneven increase in melanocytes, which produces irregular coloring or pigmentation of the skin. The sun can also cause a permanent stretching (dilation) of small blood vessels, giving your skin a mottled, reddish appearance.

Melanin is the dark brown pigment in the top layer of skin (epidermis) that gives skin its normal color. This pigment protects the deeper layers of skin from sun damage. The more melanin in the skin, the darker the skin appears and the more protection it has against sun damage.

Though people with medium or dark complexions naturally have more protection than do people with lighter complexions, they still can experience sun damage. This woman has a darker skin tone, but her face still shows signs of sun damage — irregular pigmentation and early signs of wrinkles.

Solar lentigines, also referred to as liver spots or age spots, are flat spots of increased pigmentation — usually brown, black or gray. They vary in size and usually appear on the face, hands, arms and upper back — areas most exposed to the sun. Though common in older people, solar lentigines also occur in younger adults and even in children who spend too much time in the sun.

Solar lentigines tend to become more numerous with repeated sun exposure and with advancing age. Sometimes they develop in large numbers, as seen on this man's upper back. They're different from freckles in that freckles are red or light brown, are smaller in size, tend to develop earlier in life, and usually lighten in winter months.

A dark brown lesion, called labial lentigo, can develop on the lips after repeated sun exposure. In most cases, labial lentigo is a single spot that forms on the lower lip, which is often more exposed to sunlight.

Ultraviolet radiation breaks down the skin's connective tissue — collagen and elastin fibers — which lie in the deeper layer of skin (dermis). Without the supportive connective tissue, the skin loses its strength and flexibility. This condition, known as solar elastosis, is characterized by vertical creases (A), deep wrinkles, and loose or sagging skin.

Also referred to as chloasma or "mask of pregnancy," melasma (A) is a brown darkening of facial skin. Melasma likely occurs from a combination of factors, including exposure to sunlight and an increase in the female hormones estrogen and progesterone. Melasma is very common in women who take oral contraceptives, hormone therapy or who are pregnant. The dark patches usually occur on the cheeks, forehead, nose and chin. They may or may not resolve after discontinuing the contraceptives or hormone therapy or at the end of the pregnancy.

Irregular areas of reddish-brown pigmentation characterize poikiloderma (A). This condition, which occurs most often in middle-aged women, is likely caused by chronic sun exposure in combination with sun-sensitive chemicals in cosmetics or perfume. Most often, poikiloderma appears on the side of the neck or on the cheeks.

Also known as solar keratoses, actinic keratoses appear as rough, scaly raised patches that range in color, from flesh-colored, to dark pink or brown. They're commonly found on the face, ears, lower arms and hands of fair-skinned people whose skin has been damaged by the sun. If left untreated, actinic keratoses may progress to a type of skin cancer known as squamous cell carcinoma.

Skin cancer develops mainly on areas of skin exposed to a lot of sun, including the scalp, face, lips, ears, neck, chest, arms and hands, and on the legs in women. Some types of skin cancers appear as a small growth or as a sore that bleeds, crusts over, heals and then reopens.

In the case of melanoma, an existing mole may change or a new, suspicious-looking mole may develop. One type of melanoma, known as lentigo maligna, develops in areas of long-term sun exposure and starts as dark flat spots that slowly darken and enlarge. Melanoma can develop, however, in areas not normally exposed to sunlight, such as the hair-bearing scalp, breasts, genitalia, and palms or soles. See your doctor if you notice a new skin growth, a bothersome change in your skin, a change in the appearance or texture of a mole, or a sore that doesn't heal within two weeks.