Three types of pores exist on the skin: those that enter to hair follicles, those that open to eccrine sweat glands and those that open to apocrine sweat glands. The pores that most affect acne and make pores appear large are the ones that open to hair follicles. Glands within the hair follicles, called sebaceous glands, make the oil that lubricates skin. Aspirin masks can help to clear up the oil that makes pores appear large.

A common misconception about pores is that they can “open” and “close.” Pores do not have muscles around their rims that would accomplish this task. Claims then that certain products or activities can open pores and those that suggest that astringents, for example, can close pores, are misleading. The best that can be done about large pores is to diminish their appearance.

Pore size is regulated at the most basic level by genes. When you reach puberty, the levels of various hormones in your body rise. One class of hormones called androgens cause your sebaceous glands to grow larger during this time. As the glands pump out more oil, the chances increase that a plug will form within the hair follicle’s pore. The pressure building up in the follicle and the pressure of the plug itself can stretch that pore over time.

Age affects pore size. As people age, skin loosens. Loose skin around pores can cause pores to appear larger.

The active ingredient in aspirin is a close cousin to salicylic acid, a beta hydroxy acid used to dissolve the plugs that cause blackheads and stretch pores. Masks made of aspirin have a similar effect on skin. Once the plug dissolves and the sebum trapped inside the hair follicle can flow unimpaired, the pore appears smaller.

Human skin has a pH of 4.5 to 6, which means that skin is slightly acidic. Aspirin has a pH of 5, according to Miami Museum of Science, making it slightly more acidic than most skin. This acidity is enough to have a dissolving effect on the plugs that block pores.

You can make an aspirin mask at home using nothing more than three or four crushed aspirins and warm water. Simply crush uncoated aspirin into a powder and mix in enough warm water to form a paste. Spread the mask on your skin and allow it to dry before washing it away. Note that if you have an aspirin intolerance or allergy, you should not use this mask, as the active ingredients can be absorbed through skin.

Aspirin extends anti-inflammatory benefits to skin. This is good news if your skin is inflamed due to acne.

If you do not notice improvement to your skin after using an aspirin mask, add a few drops of lemon juice or vinegar to the mask. Lemon juice has a pH of 4, while the pH of vinegar is 3.

Using the aspirin mask too often can actually cause more blackheads and, as a result of that, the appearance of larger pores. Skin needs a certain amount of sebum on its surface to remain healthy. Continually stripping away this oil forces your sebaceous gland oil production to go into overdrive. As a precaution, use the aspirin mask no more than twice per month.