Acne is so common that people often assume any old bump or blemish is just another member of the zit family. But there are lots of little skin annoyances that patients often mistake for acne. “The majority of people that come in to see me to treat their acne do in fact have acne, but there are certain conditions that can trick them,” says James Del Rosso, D.O., adjunct clinical professor of dermatology at Touro University Nevada in Henderson, Nevada, and an Acne Store advisory board member. 

While you need a professional like Dr. Del Rosso to tell you for sure, the general rules of thumb are that “if it’s a small dark spot within a dilated pore in your skin, that’s likely a blackhead. If you have a small round bump that’s filled with pus, that’s a pustule,” he says. Remember, both acne and certain other skin infections can cause pustules to form. But if it fits any of the other characteristics below, it might be something else. Here’s a quick primer on whether that blemish is acne or something else.

1. Milia

Got a little round smooth white bump? Is it hard to the touch? You might be looking at a milium (plural: milia), which is a little plug of keratin (the protein that serves as the building block of your skin) that commonly pops up around the eyes or on the cheeks and forehead. “They look like little pearls, maybe a couple of millimeters in diameter, and are more visibly well-defined than whiteheads,” describes Del Rosso. These small bumps are benign, so there’s no reason to remove them unless they bother you aesthetically. But this isn’t a DIY situation—Del Rosso says milia should be removed by a dermatologist or trained medical aesthetician. 

2. Keratosis Pilaris

This common condition is characterized by tiny rough bumps on the upper arms, thighs, buttocks, or cheeks. “Keratosis pilaris is really just a fancy term for little plugs of keratin that make their way into your hair follicles,” Del Rosso says. And they’re totally harmless. Research isn’t yet clear on why the condition pops up—genetic factors appear to play a role. [1]

When KP occurs on the face, it’s often mistaken for acne. And that’s a problem, because Del Rosso says these patients “often have sensitive skin that tends to be easily irritated. So, they're treating it with potentially drying acne products that can cause a lot of skin irritation.” So, again, if you’re not sure what you’re looking at, see your doctor before you turn to an OTC product for help.

3. Large pores

A larger pore that doesn’t have a plug of some kind on top can still look like a blackhead thanks to little bits of sebum inside that get oxidized, says Del Rosso. And some of them can contain sebaceous filaments, hair-like guides for oil that can also resemble blackheads, especially in lighter skin tones. “I saw three women in their late 20s and 30s yesterday who thought they had acne. They didn't, they just had large pores that were retaining a little sebum,” he adds. Unfortunately, nothing can shrink your pores, but a gentle chemical exfoliating ingredient like retinol or salicylic acid can help clear them or make them less visible.

4. Rosacea

You’ve likely at least heard of rosacea, a chronic inflammatory skin condition thought to be linked to genetics and environmental triggers like sunlight, stress, alcohol, and even hairspray (true story), according to the American Academy of Dermatology Association. [2] It often gets incorrectly lumped into the acne family by patients because there can be papules and pustules involved that can be red and inflamed. But Del Rosso says the difference between rosacea versus acne is that “they have redness on the central part of their face, but they don't have any blackheads or whiteheads.” 

It's not acne, but rosacea does respond to some topical and oral medications used to treat acne, according to the Mayo Clinic. [3] And warning: since skin affected by rosacea can easily be inflamed, putting anything on it without checking with your doctor first is often the wrong move.

 5. Enlarged oil glands 

When middle-aged patients come into Del Rosso’s office with small bumps on their forehead that don’t go away, they’re often enlarged oil glands known as sebaceous hyperplasia. “Sometimes the glands within our skin that produce sebum get larger—they call it hypertrophy—and they become visible,” he explains. Its cause isn’t known, but the condition is harmless and typically associated with age. Your clues that your bumps might be sebaceous hyperplasia: “They're fixed in location, and they stay—they don't come and go,” says Del Rosso. 

6. Epidermal cysts

Another condition commonly confused with straight-up acne by the untrained eye: epidermal or inflamed cysts, which Del Rosso likens to balloons underneath the skin filled with pus-like keratin. Since they don’t technically contain sebum, they aren’t actually pimples, though they do a really good impression of acne in some cases. [4] “Sometimes they'll start to leak and rupture underneath and they get more inflamed and look like an acne cyst,” Del Rosso says. And, again, it can be hard for people without a dermatology degree to tell the difference. To tell the difference between cysts and acne, Del Rosso has one guideline: “Ruptured epidermal cysts are typically much bigger, especially when inflamed and tender.”  

[1]: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3681106/

[2]:https://www.aad.org/public/diseases/rosacea/triggers/find#:~:text=Anything%20that%20causes%20your%20rosacea,%2C%20alcohol%2C%20and%20spicy%20foods.

[3]:https://www.mayoclinic.org/diseases-conditions/rosacea/diagnosis-treatment/drc-20353820

[4]: https://www.ncbi.nlm.nih.gov/books/NBK532310/