Aspirin is one of the most widely used drugs in the world. It was created from a plant-derived chemical called salicylate, which people frequently used in the 18th century to reduce the fever, pain, and inflammation caused by diseases such as rheumatic fever and rheumatoid arthritis. However, salicylate caused side effects that often would prevent people from using it. Therefore, in 1895, Frederick Bayer of Bayer pharmaceuticals altered the chemical structure of salicylate to create a new form of salicylate that did not cause side effects. With these alterations, salicylate became acetylsalicylic acid, which is more commonly known as aspirin.1
The structure of aspirin is similar to that of salicylic acid, which is a common acid used in the topical treatment of acne. When aspirin is placed in water, it breaks down into (1) salicylic acid and (2) acetic acid. For this reason, some people try dissolving aspirin pills in water at home and applying the watery paste to their skin in an attempt to help reduce acne.
When applied topically, salicylic acid promotes shedding of surface skin cells. Further, scientists have found that topical salicylic acid is anti-inflammatory. Both of these mechanisms can help reduce acne. Because of the similarities between aspirin and salicylic acid, it is likely that aspirin may provide the same effects as salicylic acid when dissolved in water and applied topically.2,3
For safety reasons, salicylic acid is allowed in strengths up to 2% in over-the-counter products in the United States. It is also found in higher percentages in professionally-administered 20% and 30% salicylic acid chemical peels, which are left on the skin for only a short period of time and then washed off. These higher-percentage salicylic acid peels must be administered by an esthetician, nurse, or doctor.5,6
When aspirin is placed in water, at least 4% of it gets converted into salicylic acid. For instance, a 325mg aspirin tablet would yield 13mg of salicylic acid when placed in water. However, the amount of aspirin converted into salicylic acid may be higher than 4% depending on the type of aspirin, for instance, if non-controlled-release aspirin tablets are used.
Because dissolving aspirin at home in water is unscientific, and aspirin tablets may vary in their ability to release salicylic acid, it is possible to obtain amounts of salicylic acid that are higher than the legal limit allowed over-the-counter. While this may sound like it would make it more effective, it can be dangerous for multiple reasons. First, you can give your skin a chemical burn. Also, if you put too much salicylic acid on a large area of skin for a prolonged period of time, it can become a life-threatening, systemic issue, which can result in major complications.4,5
The Science: What Clinical Studies Tell Us
When dissolved in water, topical aspirin might help somewhat with acne since it is similar to salicylic acid, which works moderately well in the treatment of acne. However, to know whether dissolved topical aspirin is effective or not, we first need to read clinical trials, but there are no direct trials as such on acne, so we cannot say for sure whether topical aspirin will have effects similar to topical salicylic acid.
Scientists have studied, though, the effects of topical aspirin on skin inflammation in two studies. This is somewhat interesting to us because acne is an inflammatory disease. In both studies, the topical aspirin did not help when used to treat inflammation after the inflammation had already started, but did help prevent some inflammation when administered to the skin before inflammation began. Since acne is, at its root, an inflammatory disease, we can infer that topical aspirin may not be effective in reducing existing inflammation, but may be helpful in preventing some of it.6 In other words, topical aspirin might not help reduce inflammation from acne already on the skin, but might help prevent some inflammation that could lead to the development of acne.
Side Effects of Salicylic Acid and Topical Aspirin
Research on topical aspirin has found it to be a relatively safe drug with no reported side effects when applied in controlled and small doses. The same is true of salicylic acid. At over-the-counter dosages, salicylic acid can cause dryness and peeling in up to 1/3 of people who use it.7-10
However, since aspirin can break down into salicylic acid, and theoretically someone could dissolve many aspirin pills at once and then apply it to the skin, it is important to examine the side effects of salicylic acid when administered in higher doses. At high concentrations, salicylic acid can cause burns to the skin. Also, when applied over large parts of the body, and when left on the skin for extended periods of time, salicylic acid can cause serious, systemic problems, leading to hospitalization.
Because it is difficult to accurately calculate the amount of salicylic acid you will get when dissolving aspirin in water, combined with the fact that research on topical aspirin is completely lacking when it comes to acne, it is best to simply purchase over-the-counter salicylic acid at a safe percentage, up to 2%, and eliminate the trouble and risk of dissolving aspirin pills. Salicylic acid is readily available over-the-counter and inexpensive.