Cystic acne forms when a clogged pore becomes deeply infected and inflamed, creating a painful, swollen lump beneath the skin’s surface. Unlike regular pimples that sit near the top of the skin, cysts develop in the dermis, the skin’s middle layer, where the infection triggers an intense immune response. The process involves a chain reaction of excess oil, trapped bacteria, and hormonal signals that can take weeks or months to build up.
What Happens Inside the Pore
Every cystic breakout starts the same way a regular pimple does: a pore gets clogged. Your skin naturally produces oil (sebum) to stay moisturized, and dead skin cells are constantly being shed inside hair follicles. When too much oil mixes with too many dead cells, the mixture forms a tiny plug called a microcomedone. At this stage, you can’t see or feel anything on the surface.
What separates cystic acne from a standard whitehead is what happens next. Bacteria that normally live on your skin, primarily a species called Cutibacterium acnes, get trapped behind that plug and begin multiplying in the oil-rich, oxygen-poor environment. As the bacterial population grows, the walls of the follicle weaken under pressure. Eventually, the follicle wall ruptures, and its contents (bacteria, oil, dead cells) spill into the surrounding tissue deep in the dermis.
Your immune system responds aggressively. Skin cells activate inflammatory signaling pathways that flood the area with immune molecules, recruiting white blood cells to fight the infection. This creates the hallmark features of a cyst: a large, red, painful lump filled with pus that can linger for weeks. The inflammation runs so deep that cystic lesions frequently leave permanent scars, even when left completely alone.
Hormones Are the Primary Driver
Androgens, a group of hormones that includes testosterone, are the main fuel behind cystic acne. They directly stimulate your oil glands to grow larger and produce more sebum. The more sebum your skin makes, the more likely pores are to clog and the more food bacteria have to thrive on. Early experiments showed that prepubertal boys given testosterone injections developed significantly increased sebum production and enlarged oil glands, confirming the direct link.
A particularly potent androgen called dihydrotestosterone (DHT) is considered the key player. DHT is 5 to 10 times more potent than testosterone at activating oil glands. Your skin can actually manufacture its own androgens locally, converting a precursor hormone called DHEA-S into active androgens right inside the oil gland itself. This is one reason you can develop cystic acne even when blood hormone levels appear normal on lab tests.
This hormonal connection explains why cystic acne peaks during puberty, when androgen levels surge, and why it commonly flares around menstrual periods, during pregnancy, or with conditions like polycystic ovary syndrome (PCOS). It also explains why some people are simply more prone than others: genetics determine how sensitive your oil glands are to androgens, and that sensitivity varies enormously from person to person.
How Stress Feeds the Cycle
Stress doesn’t just make existing acne feel worse. It actively drives oil production through a specific hormonal pathway. When you’re stressed, your body produces corticotropin-releasing hormone (CRH) and cortisol. Researchers have found very strong expression of CRH in the oil glands of acne-affected skin compared to clear skin. CRH stimulates sebum production and, critically, it also increases the activity of an enzyme that converts inactive hormones into active androgens within the skin. So stress effectively amplifies the same androgen-driven process that causes cystic acne in the first place.
Diet’s Role in Sebum and Skin Cell Growth
High-glycemic foods, things like white bread, sugary drinks, white rice, and pastries, can worsen cystic acne through a well-documented hormonal cascade. Eating these foods causes a rapid spike in blood sugar, which triggers your pancreas to release large amounts of insulin. Chronically elevated insulin raises levels of a growth signal called insulin-like growth factor 1 (IGF-1) while lowering the proteins that normally keep IGF-1 in check.
IGF-1 is a potent growth promoter for virtually all body tissues. In the skin, it does two things that set the stage for cysts. First, it stimulates oil glands to produce more sebum. Second, it accelerates the turnover of skin cells lining the inside of pores, causing them to multiply and shed faster than normal. This combination of excess oil and excess dead cells is exactly what creates the plugs that start the cystic acne process.
Dairy, particularly skim milk, appears to work through a similar mechanism. Milk contains its own IGF-1 and other growth factors that can activate the same signaling pathways, promoting both oil production and skin cell overgrowth. The effect isn’t dramatic enough that cutting dairy will clear severe cystic acne on its own, but it can be a meaningful contributing factor for some people.
Medications That Can Trigger Breakouts
Several classes of drugs are known to cause or significantly worsen cystic acne. Oral corticosteroids are among the most common culprits, partly because they increase yeast growth within hair follicles and partly because they alter hormone levels. Anabolic steroids, including testosterone supplements and bodybuilding compounds like stanozolol and nandrolone, can cause severe acne including the most extreme forms.
Some hormonal contraceptives can go either way. Combination birth control pills often improve acne, but progesterone-only methods, including certain injections, implants, and hormonal IUDs, can aggravate it by reducing levels of a protein that binds up free testosterone. Other medications linked to acne flares include:
- Antiepileptics like carbamazepine and phenytoin
- Lithium and certain antidepressants
- B vitamins, particularly B6 and B12 in high doses
- Immunosuppressants like cyclosporine
If your cystic acne appeared or worsened after starting a new medication, that timing is worth noting and discussing with whoever prescribed it.
Physical and Environmental Triggers
Friction and pressure on the skin can push oil and bacteria deeper into pores, a phenomenon sometimes called acne mechanica. Helmet straps, tight headbands, chin straps, bra straps, and even the habit of resting your chin on your hand can create localized cystic breakouts in areas that wouldn’t otherwise be affected. Phone screens pressed against the jawline are another common offender.
Humidity and sweating increase oil on the skin’s surface and can accelerate pore clogging, which is why cystic acne often worsens in summer or in people who work in hot environments. Occlusive skincare products and heavy makeup can have a similar effect by trapping oil and dead cells against the skin.
Why Some People Get Cysts While Others Don’t
Most teenagers deal with some form of acne, but only a fraction develop the deep, cystic variety. The difference comes down to a few factors working together. Genetics play the largest role: if one or both of your parents had cystic acne, your risk is substantially higher. What’s inherited isn’t just a tendency toward oily skin but also how aggressively your immune system responds to bacteria inside a clogged pore. Some people’s immune systems mount a proportional response that stays near the skin’s surface, producing a standard pimple. Others mount an outsized inflammatory reaction deep in the dermis, producing cysts.
Oil gland sensitivity to androgens is also inherited. Two people with identical hormone levels can have vastly different acne because one person’s oil glands respond much more strongly to the same amount of testosterone or DHT. This is why cystic acne can run in families even when no one has an underlying hormonal disorder. The combination of genetically sensitive oil glands, a strong inflammatory response, and any of the triggers above, whether hormonal shifts, stress, diet, or medications, creates the conditions for cysts to form repeatedly.