Aspirin, which costs pennies a pill, stacks up better than many of the thousand dollar per dose medications that are used to treat heart attacks. Furthermore, aspirin has been shown to reduce the risks of heart attacks, strokes, colon, breast and prostate cancer and possibly even melanoma in women.
Sure aspirin is a wonder drug: cheap and effective against many awful conditions. But aspirin is still a drug and like any drug it has some side effects. Like other blood thinners, aspirin can cause minor as well as major side effects. Nose bleeds are usually (but not always ) minor and so is a tendency toward easy bruising. However, aspirin can cause bleeding stomach ulcer or bleeding in the brain, neither of which is minor and at times can cause death. Certain persons, especially those with asthma, are more likely to be allergic to aspirin. Usually the allergies are minor with a drug rash, but rarely aspirin allergic patients develop anaphylaxis, which swells the airways and can cause death.
Given that aspirin use has potential serious side effects, not everybody should be taking this drug. If you have for example heart disease such as a heart attack or angina, then the risks of taking aspirin (assuming you are not allergic to aspirin) might be worth the benefits it offers in reducing your heart attack risk. Similar cases can be made for patients who have high cholesterol, high blood pressure, strong family history of heart disease or colon cancer or who smoke.
Yet for the rest of the population,which by the way is a good chunk of America, the risks are simply not worth it. For example, a healthy twenty something would stand little to gain from taking aspirin as his or her risk of developing heart disease or certain cancers for the forseeable future is quite small. On the other hand, the risks of aspirin for this individual are the same as for the 70 year heart disease patient, with the exception that the young dude doesn’t really reduce his already low risks for certain diseases.
As far as preventing melanoma is concerned, there are less riskier ways to do this. Wear sun screen whenever outdoors and have suspicious lesions checked by your doctor.