Dr. Alai is an actively practicing medical and surgical dermatologist in south Orange County, California. She has been a professor of dermatology and family medicine at the University of California, Irvine since 2000. She is U.S. board-certified in dermatology, a 10-year-certified fellow of the American Academy of Dermatology, and Fellow of the American Society of Mohs Surgery.
Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.
Freckles are thought to develop as a result of a combination of genetic tendency (inheritance) and sun exposure. Two people receiving the same sun exposure may not have an equal chance of developing freckles. Natural sunlight and artificial suntanning lights emit ultraviolet (UV) rays. After exposure to ultraviolet rays, the outer layer of the skin (the epidermis) thickens and the pigment-producing cells (the melanocytes) produce the pigment melanin at an increased rate. (This production of melanin may in fact give some protection against future sun exposure.)
Of course, people differ a great deal in their reaction to sunlight. To take an extreme example, there is no pigmentation in the skin of an albino because of a defect in melanin metabolism. On the other hand, people with dark complexions are relatively less sensitive to sun exposure than fair-skinned people. However, people with dark skin are not entirely resistant to the effects of the sun, and they, too, can become sunburned with prolonged exposure. People with blond or red hair, light-colored eyes, and fair skin are especially susceptible to the damaging effect of UV rays.
Irrespective of skin color, freckling is caused by the uneven distribution of the melanin pigment in the skin.. A freckle is essentially nothing more than an unusually heavy deposit of melanin at one spot in the skin.
How important is heredity with freckles?
Heredity and skin type are very important factors for the tendency to develop freckles. Freckles tend to be inherited genetically and are most common in individuals with fair skin and/or with blond or red hair.
Research in twin siblings, including pairs of identical twins and pairs of fraternal (nonidentical) twins, have found a striking similarity in the total number of freckles found on each pair of identical twins. Such similarities were considerably less common in fraternal twins. These studies strongly suggest that the occurrence of freckles is influenced by genetic factors. In fact, the variations in freckle counts appear to be due largely to heredity.
Ongoing research in a rare disease called xeroderma pigmentosum has also confirmed the genetic tendency of freckles. Excessive freckles in dark-haired individuals are quite common in this disease.
Skin cancer is the most common form of cancer
in humans. There are three main types of skin cancer; basal cell carcinoma and
squamous cell carcinoma (the nonmelanoma skin cancers), and melanoma.
Melanoma is a type of skin cancer which begins in skin cells called melanocytes and affects more than 53,600 people in the United States each year. These melanocytes can grow together to form benign moles which, after a change in size, shape, or color can be a sign of melanoma. Caused by sun exposure, early detection becomes extremely important to avoid a spread to other areas of the body. Diagnosis is confirmed through a biopsy of the abnormal skin and treatment depends on the extent and characteristics of the patient.
Moles are small skin growths that may appear flat or raised and are often tan, brown, black, reddish brown, or skin colored. They are typically about the size of a pencil eraser. There are three types of moles. Monthly skin self-exams are essential in the early detection of abnormal moles and melanomas.
Sun sensitivity (photosensitivity) is an inflammation of the skin induced by the combination of medications or substances and sunlight. The affect on the skin is redness, which looks similar to a sunburn. Generally, these reactions are either phototoxic or photoallergic. Phototoxic drugs are more common than photoallergic drugs. Symptoms of phototoxic reactions are a burning and stinging sensation and then redness. Symptoms of photoallergic reactions are itching, redness, swelling, blisters of the affected area. Treatment generally is discontinuation of the medication and topical application of creams.
Sunburn is caused by overexposure to UV radiation from the sun. UV rays can also damage the eyes. Repeated overexposure to UV rays also increases the risk for scarring, freckles, wrinkles, and dry skin. Symptoms of sunburn include painful, red, tender, and hot skin. The skin may blister, swell, and peel. Sun poisoning (severe sunburn) include nausea, fever, chills, rapid pulse, dizziness and more. Treatment for sunburn depends upon the severity. Sun protection and sunscreen for an individual's skin type is recommended to decrease the chance of sunburn.
Sunscreens are crucial for sun protection. Sun damage to the skin from exposure to ultraviolet rays is a risk factor for skin cancer and melanoma. To avoid sunburn, people should limit sun exposure during the peak hours of 10 a.m. to 3 p.m., wear protective clothing, and use a sunscreen. People with sensitive skin should use a sunscreen with an SPF of 30 or more.
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