Why do blemishes become red and sore?

Beneath the surface · Part four

Beneath the surface In Part three, we looked at how oil and dead skin cells collect inside a hair follicle to form a blockage.

Sometimes that blockage just sits there as a standard blackhead or whitehead. But other times, seemingly overnight, it becomes red, swollen, and incredibly sore.

So, what changed?

Why do teenage blemishes become red and sore?

First things first: blemishes are not caused by dirty skin.

Acne actually develops through a perfect storm of biological processes happening all at once. We are talking about increased oil production, changes in how your skin sheds dead cells, and the behavior of a microbe called Cutibacterium acnes. Recent research even suggests that a general imbalance in your skin's natural microbiome plays a massive role (Dréno et al., 2024).

Despite its intimidating name, C. acnes isn't a "bad" bacterium. It naturally lives on healthy skin, and its presence alone doesn't trigger breakouts.

But inside an oily, clogged follicle, the environment completely shifts. Changes in the specific strains of C. acnes throw off the balance of the wider skin microbiome, which triggers an inflammatory response (Dréno et al., 2024).

Your immune system rushes to the scene.

Suddenly, that quiet, blocked pore becomes a red, swollen, and sore blemish — often developing a visible white or yellow center. That is the inflamed blemish you ultimately see on the surface.

What does this mean for teenage blemish skincare?

The answer is never harder scrubbing.

Official guidance from NICE recommends cleansing acne-prone skin just twice a day with a gentle, non-alkaline cleanser. Picking and scratching? Best avoided — unless you want to significantly increase the risk of permanent scarring.

For teenagers, a simple routine makes the most sense. You don't need a complicated ten-step ritual to get results.

A solid morning and evening wash with something like the Upenya Exfoliating Cleanser does the heavy lifting. Even oily skin, needs hydration, so moisturise thoroughly with a lightweight moisturiser, like the Upenya Moisturising Gel. From there, you can follow up with a targeted treatment, like Upenya Blemish Care with salicylic acid,  to handle the stubborn, blemish-prone areas. And there is one message worth repeating to both teenagers and stressed-out parents: blemishes are not proof of poor hygiene.

Puberty completely alters oil production and the environment inside the hair follicle. When inflammation kicks in, a quiet blocked pore can turn into an angry-looking spot right before school photos.

Annoying? Absolutely.

A sign that your teenager needs to scrub harder? Not at all.

Blackheads, whiteheads, and red pimples all begin in the exact same place — a blocked hair follicle. What happens beneath the surface determines what eventually appears on top.

Gentle cleansing, consistent skincare, and less picking are far more sensible than declaring war on every new spot.

Frequently asked questions

Is a red teenage blemish an infection?

Not necessarily. C. acnes naturally lives on healthy skin. Acne involves a mix of oil production, blocked follicles, and inflammation rather than being a simple skin infection (Dréno et al., 2024).

Should teenagers wash their faces more when they have blemishes?

No. NICE recommends cleansing acne-prone skin twice daily with a suitable, gentle cleanser (NICE, 2026). More washing and aggressive scrubbing will only irritate the skin further.

Should teenagers squeeze blemishes?

It is best avoided. Persistent picking or scratching breaks the skin barrier and heavily increases the risk of scarring (NICE, 2026).

When should my teenager see a doctor or dermatologist?

Seek medical advice if blemishes become severe or painful, deep nodules or cysts develop, or the condition starts affecting your teenager’s emotional wellbeing. The risk of scarring increases the longer severe acne goes untreated (NICE, 2026).

References

Dréno, B., Dekio, I., Baldwin, H., Demessant, A.L., Dagnelie, M.A., Khammari, A. and Corvec, S. (2024) ‘Acne microbiome: From phyla to phylotypes’, Journal of the European Academy of Dermatology and Venereology, 38(4), pp. 657–664. doi: 10.1111/jdv.19540.

National Institute for Health and Care Excellence (NICE) (2026) Acne vulgaris: management. NICE guideline NG198. Available at: nice.org.uk (Accessed: 8 September 2026).