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Blood is approximately twice as thick as water because of the cells and other components found in it.
IgA antibodies protect body surfaces exposed to outside foreign substances. IgG antibodies are found in all body fluids. IgM antibodies are the first type of antibody made in response to an infection. IgE antibody levels are often high in people with allergies. IgD antibodies are found in tissues lining the abdomen and chest.
More than 50% of American adults have oral herpes, which is commonly known as "cold sores" or "fever blisters." The herpes virus can be active on the skin surface without showing any signs or causing any symptoms.
The average adult has about 21 square feet of skin.
Pubic lice (crabs) are usually spread through sexual contact. You cannot catch them by using a public toilet.