ACNE: What it is, Why it happens, and What Actually Works.

A GP's honest guide to understanding your skin and building a routine that makes a real difference

So, what exactly is acne?

Acne is one of the most common skin conditions I see, both in my GP clinic and through messages I get on Instagram. And yet it’s also one of the most misunderstood, mostly because people assume it’s a teenage problem, or a hygiene problem, or something you should just be able to clear up with a good cleanser. None of that is true.

Acne happens when hair follicles become blocked with oil and dead skin cells. That blockage creates the perfect environment for a bacteria called Cutibacterium acnes to multiply, which triggers inflammation. The result is everything from small whiteheads and blackheads through to deeper, painful cysts that can leave scarring if they’re not treated properly.

It can affect your face, chest, back and shoulders. It can start in your teens and clear up, or it can show up for the first time in your 30s. It can be mild and occasional or persistent and deeply affecting. I see patients who have had acne for twenty years and have tried everything. I also see teenagers who are mortified by a few spots and don’t know where to start.

Wherever you are on that spectrum, there is something that will help. The key is understanding what’s driving it for you.

And why does it happen?

Understanding what’s driving your acne matters because it shapes how you treat it. The same spot cream isn’t going to work the same way for a 16 year old with oily skin as it will for a 38 year old whose acne started after coming off the pill. There are four main drivers and most people with acne have a combination of them.

Excess sebum production.

Your skin produces oil naturally and needs it. But some skin, often genetically, produces more than it needs. That excess oil mixes with dead skin cells and blocks the follicle.

Dead skin cell buildup.

Skin sheds constantly but sometimes that process doesn’t happen efficiently enough and cells accumulate in the pore instead of shedding properly.

Bacteria.

Cutibacterium acnes lives on all of our skin but in a blocked, oily follicle it multiplies rapidly and triggers an immune response, which is what causes the redness and swelling.

Hormones.

This is the big one that gets underestimated, especially in adults. Androgens, which both men and women produce, stimulate the sebaceous glands to produce more oil. This is why acne often spikes around your period, during pregnancy, after coming off the pill, and in perimenopause. It’s also why stress makes acne worse, cortisol drives androgen production.

Common mistakes that make acne worse

This is the section I wish more people read before they spend a fortune on products that aren’t helping.

Over-cleansing and over-exfoliating.

I see this constantly. People assume acne is caused by dirty skin so they cleanse three times a day, use harsh scrubs, and strip their skin back as far as it will go. What actually happens is you destroy your skin barrier, trigger more oil production as the skin tries to compensate, and end up more inflamed than when you started. Twice daily cleansing with a gentle, non-stripping cleanser is enough.

Skipping moisturiser.

Acne-prone skin still needs hydration. Skipping it because you think your skin is oily enough is one of the most common mistakes I see. Dehydrated skin produces more oil to compensate. A lightweight, non-comedogenic moisturiser is non-negotiable.

Using too many actives at once.

Retinoids, acids, benzoyl peroxide, niacinamide, vitamin C. All useful. All potentially irritating if you pile them on together before your skin has had a chance to adjust. I’d rather you use one thing consistently than five things chaotically.

Picking.

I know. Everyone knows. But it genuinely makes things worse, spreads bacteria, and is one of the main causes of post-acne scarring and pigmentation. If you have a cyst, leave it alone or come and see someone.

Changing your routine too often.

Acne treatments take time, and I mean real time. Most people need a solid three months of consistent use before they start to see meaningful change, and even then you’re at the beginning, not the end. There is no quick fix here, no matter what the packaging says. Switching products every few weeks because something isn’t working yet is one of the most common reasons people feel like nothing ever works for them. Pick a routine, stick to it, give it the time it deserves.

Close up of a face with acne on cheek and info-icon with circles and a line indicating the acne with a light grey transparent overlay.

When to see a doctor

This is the part most skincare brands won’t tell you, because they’d rather sell you another product. But as a GP, I have to be honest with you.

There are situations where no serum or cleanser is going to be enough on its own, and the kindest thing I can do is tell you that clearly rather than let you spend years and a lot of money finding it out yourself.

go and see your gp if:

Your acne is painful, cystic, or deep under the skin. Nodular and cystic acne causes scarring. It needs prescription treatment, often a combination of topical and oral medication, and in some cases isotretinoin. Skincare alone will not shift it.

You’ve had consistent acne for more than three months and over the counter products haven’t made a meaningful difference. Three months is a fair trial. If nothing is shifting after that, it’s time to get proper help.

Your acne is leaving marks, scars, or pigmentation behind. This tells you the inflammation is significant enough to cause damage. That needs to be managed medically, not just topically.

Your acne started or significantly worsened in adulthood, especially around hormonal changes. Coming off the pill, pregnancy, postpartum, perimenopause. This often has a hormonal driver that needs to be investigated and potentially treated hormonally, not just topically.

Your acne is affecting your mental health. This one matters as much as the physical. I have patients who won’t leave the house on bad skin days, who’ve stopped socialising, who feel genuinely low because of their skin. That is reason enough to come in. You don’t have to be at a clinical threshold to deserve help.

Your GP can prescribe topical retinoids, topical and oral antibiotics, azelaic acid, the contraceptive pill for hormonal acne, spironolactone in some cases, and refer you for isotretinoin if needed. These are effective treatments. Use them.

building your routine - teenage acne

Blemish Control Cleanser
€16,00

BY CeraVe

2% Salicylic Acid

Blemish Control Gel
€18,00

BY CeraVe

2% Salicylic Acid

BHA Blackhead Power Liquid
€33,00

BY COSRX

Salicylic Acid

The Ceramide Skin Barrier Moisturiser
€24,00

BY COSRX

Ceramide Barrier Support

LaRochePosay-Product-Skincare-Effaclar-Azgelcream-Texture

Effaclar A.Z Gel Cream
€43,00

BY La Roche-Posay

Azelaic Acid

Mela B3 Dark Spot Serum
From €55,00

BY La Roche-Posay

10% Niacinamide

Choose Options

Effaclar H Iso-Biome Cleansing Cream
€18,00

BY La Roche-Posay

Glycerin

La Roche-Posay Effaclar Duo+M Patch packaging on a white background

Effaclar Duo+M Patch
€13,00

BY La Roche-Posay

Hydrocolloid Technology

building your routine: teenage acne

For teenagers, the approach is actually simpler than most people think. The temptation is to buy every acne product on the shelf but that’s almost always counterproductive. Here’s what I recommend starting with.

CLEANSERS:
A gentle, non-stripping cleanser. Not a harsh foaming acne wash. Stripping your skin makes things worse, not better. This is the foundation of everything. If you want a cleanser with a bit more active work in it, the CeraVe Blemish Control Cleanser is a good option. It contains salicylic acid but is still gentle enough for daily use. The Skingredients Preprobiotic Cleanser is another one I like, super gentle and leaves the skin feeling nice and hydrated rather than stripped.

HERO PRODUCTCS:

Our hero products for teenage acne are not what you’d expect. I’m not reaching for the strongest acne treatments here. I’m reaching for things that work with the skin rather than against it.

SERUMS

La Roche Posay Mela B3 serum is one I use a lot in this context. It targets inflammation, regulates oil, and improves skin texture without being aggressive. La Roche-Posay Effaclar AZ Gel Cream is another favourite, azelaic acid based, well tolerated, and genuinely effective for mild to moderate acne. Add one at a time. Give each one a full month before you add anything else.

MOISTURISERS:

For moisturiser I really like the La Roche-Posay Effaclar H Isobiome for acne-prone teenage skin. It’s designed specifically for skin that’s been compromised by acne treatments and it’s brilliant at maintaining the barrier without causing breakouts.

RETINOL:

In the evening, once your skin has adjusted to the above, CeraVe Resurfacing Retinol Serum is a good entry point into retinoids. Start two nights a week maximum. It will likely cause some dryness initially. That’s normal.

One important thing on timing. In the first four to six weeks of starting any new active, whether that’s a retinoid, azelaic acid, or a BHA, you may actually see things get worse before they get better. This is completely normal and it doesn’t mean the product isn’t working. Stick with it, keep the rest of your routine simple, and give it the full three months before you make any judgements.

SPF every single morning. Every morning. No exceptions. My favourite for acne-prone teens is the TOCOBO Bio Watery Sun Cream SPF 50+.

Add one product at a time. Always.

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ADULT & HORMONAL ACNE

This is where I have to be really honest with you. Adult hormonal acne is one of the most frustrating things to self-treat because the driver is internal, not just on the surface of your skin. Skincare alone is rarely enough.

If your acne started or got significantly worse in adulthood, around coming off the pill, postpartum, or in perimenopause, please go and see your GP before spending a lot of money on products. There are really effective prescription options and getting the right one makes everything else work better.

That said, the products below can help and are worth trying while you’re waiting for an appointment or alongside whatever you’ve been prescribed.

ADULT ACNE RECOMMENDATIONS

€145,00

This is one of our go tos in clinic for acne. Use under your prescription creams AM and PM.

View Product

€43,00

A blend of azaelic acid and salicylic acid, its great for adult acne.

View Product

€185,00

A combination of retinoid and salicylic acid, for mild cases of adult acne and blemishes.

View Product

if you are seeing your own doctor and on meds, then this is for you.

WHAT TO USE ALONGSIDE PRESCRIPTION TREATMENTS

The key principle is keep it simple. When you’re on a prescription treatment, whether that’s a topical retinoid, an antibiotic cream, azelaic acid, or something like isotretinoin, your skin is already doing a lot of work. You don’t need to layer ten actives on top.

What we typically recommend in clinic is this. A gentle non-stripping cleanser morning and evening. A good serum underneath your prescription treatment. We often use Mela B3 or SkinCeuticals Metacell Renewal B3 here, applied first and left to absorb before your prescription cream goes on top. This combination genuinely helps with tolerability and supports the skin barrier while the prescription does its job. Then a good moisturiser. Then SPF in the morning, always, but especially on anything that increases photosensitivity.

The serum underneath the prescription is something a lot of people don’t know to do. It helps reduce dryness and irritation and keeps your skin in better condition throughout treatment.

If your skin is very reactive, strip right back. Cleanser, moisturiser, SPF only, until things settle. Then add back in gradually.

If you’ve been prescribed isotretinoin, I’ve written a separate guide specifically for that. The skincare needs on Roaccutane are quite different and it deserves its own page.

read about our roaccutane recommendations

The Questions We Get Asked Most about acne

Diet and acne is a complicated area and the research is still evolving. There is some evidence that high glycaemic foods and dairy, particularly skimmed milk, can worsen acne in some people. But it’s very individual. I wouldn’t tell you to completely overhaul your diet before trying anything else, but if you notice a consistent pattern between certain foods and flare ups, that’s worth paying attention to. Food alone is rarely the whole answer.
Yes. Look for non-comedogenic on the label, which means it’s formulated not to block pores. Mineral-based foundations tend to work well for acne-prone skin. The more important thing is taking it off properly at the end of the day. Double cleansing if you’re wearing SPF and makeup is a good habit.
No. Physical scrubbing on active acne spreads bacteria, causes micro-tears in the skin, and makes inflammation worse. Chemical exfoliation, so salicylic acid or a gentle BHA, is a much better way to keep pores clear without the damage.
Most of the dark marks left after spots are post-inflammatory hyperpigmentation, not true scarring. The good news is that PIH fades with time and responds well to ingredients like niacinamide, azelaic acid, and vitamin C. True scarring, the textural kind, is a different thing and may need clinic treatment. SPF is essential for both because sun exposure makes pigmentation significantly worse.
Go and see your GP. I mean that genuinely, not as a throwaway line. If you’ve been consistent with a good routine for three months and nothing is shifting, there is almost certainly a prescription treatment that will help. You don’t have to just live with it.
It can be. Stress triggers cortisol, which drives androgen production, which increases sebum. So yes, stress can absolutely worsen acne. That doesn’t mean the answer is just to relax, that’s not particularly helpful advice. But it does mean that if you’re going through a difficult period and your skin is flaring, there’s a real biological reason for it.
If their acne is affecting their confidence or daily life, at any age. There’s no threshold they need to reach before they deserve help. Early treatment also means less risk of scarring, so sooner is genuinely better.