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Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
The most common childhood diseases include croup, chickenpox, ear infections, flu, pneumonia, ringworm, respiratory syncytial virus, scabies, head lice, and asthma.
Astigmatism is the most common vision problem. It may accompany nearsightedness or farsightedness. It is usually caused by an irregularly shaped cornea, but sometimes it is the result of an irregularly shaped lens. Either type can be corrected by eyeglasses, contact lenses, or refractive surgery.
Limit intake of red meat and dairy products made with whole milk. Choose skim milk, low-fat or fat-free dairy products. Limit fried food. Use healthy oils when cooking.
Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.