What’s Inside a Pimple? A Dermatologist Explains
What even is that white stuff — and why is it inside some pimples, but not others?
Published:
3 minute read
If you’re a Dr. Pimple Popper fan, you’re probably familiar with how pimples form and move through their stages, from clogged pore to visible breakout. But most people aren’t really familiar with exactly what’s inside a pimple — why it’s sometimes just a hard bump, what it means when it’s red or painful, or why it sometimes turns into an oozy mess that’s so hard to leave alone.
To clear things up, we asked dermatologist and SLMD founder Sandra Lee, MD (aka Dr. Pimple Popper) to explain what’s really happening under the skin.
Fast facts: what’s inside a pimple
- Every pimple starts with a clogged pore
- What's inside depends on whether inflammation develops
- Pus forms only in certain types of inflamed pimples
What’s inside blackheads and whiteheads
“A pimple always starts with a clogged pore,” explains Dr. Lee. “What happens next — and what ends up inside — depends on whether inflammation develops.”
Blackheads and whiteheads are non-inflammatory acne. In both cases, the pore is clogged with dead skin cells and oil (sebum), but there’s no infection and no pus.
Blackheads
What they are: clogged pores that remain open, so they oxidize and turn dark
What’s inside: dead skin cells and oil
Whiteheads
What they are: clogged pores that are covered by a thin layer of skin
What’s inside: dead skin cells and oil
Despite the name, whiteheads do not contain pus. They are simply blocked pores that have not become inflamed.
Dr. Pimple Popper's Pimple Stoppers
What’s inside an inflamed pimple
“When bacteria get trapped inside a clogged pore, your immune system steps in to fight it,” explains Dr. Lee. That reaction is what causes redness, swelling, and tenderness. If the response becomes stronger, white blood cells build up and form pus, mixed with bacteria, oil, and debris.
Papules
What they are: red, tender bumps that do not contain pus
What’s inside: dead skin cells, oil, bacteria, and inflamed tissue
Nodules
What they are: deep, swollen areas of inflammation that do not contain pus
What’s inside: bacteria and inflamed tissue deep within the skin
Pustules
What they are: inflamed pimples filled with pus
What’s inside: dead skin cells, oil, bacteria, and white blood cells (pus)
Cysts
What they are: deeper, larger pimples that contain pus
What’s inside: oil, bacteria, inflamed tissue, and white blood cells (pus)
Why popping pimples causes more damage
Pimples are part of your skin’s natural healing process. When bacteria and debris build up inside a pore, your body works to clear it out and repair the skin.
Popping disrupts that process. Squeezing or picking can push bacteria deeper into the skin, increase inflammation, and damage surrounding tissue. This can lead to longer healing time, dark marks, and permanent acne scarring, which is why dermatologists like Dr. Lee discourage pimple popping. Instead, treat and prevent acne with an acne-fighting routine.
Try: SLMD Acne Essentials Routine, SLMD Acne System
Dr. Pimple Popper’s pimple-stopping picks
Instead of popping, treating pimples based on what’s inside can help calm inflammation and support healing.
- Salicylic acid helps clear dead skin cells and oil from clogged pores, making it best for blackheads and whiteheads. Try: SLMD Salicylic Acid Spot Treatment, Salicylic Acid Pimple Patches
- Benzoyl peroxide helps reduce acne-causing bacteria and inflammation, making it best for red, inflamed, or pus-filled pimples. Try: SLMD BP Acne Spot Treatment
Acne FAQ: what’s inside a pimple
Q: What is the white stuff inside a pimple?
A: Pus is a buildup of white blood cells mixed with bacteria, oil, and debris that forms when inflammation intensifies inside a clogged pore.
Q: Why do some pimples have pus and others don’t?
A: Blackheads and whiteheads don’t contain pus. Pustules and many cysts do, because the immune response is stronger.
Q: Why are some pimples hard and painful but never come to a head?
A: Papules and nodules involve deeper inflammation that does not always produce a visible pocket of pus.
Q: What happens if you pop a pimple?
A: Popping can push bacteria and inflammation deeper into the skin and increase the risk of dark marks and acne scarring.
Dr. Lee's Last Word
Pimples are a normal skin response to a clogged pore. Understanding what's happening inside can hep you treat breakouts correctly and avoid unnecessary irritation or damage.
