What Causes Acne? 7 Common Causes Explained by a Dermatologist

Written by Dr. Nidhi Gupta
MD Dermatology • Updated August 2026

Acne affects teenagers and adults alike, yet one question continues to come up: what actually causes acne?

It's easy to blame one product, one food or one stressful week for a breakout. In reality, acne is usually more complicated.

Acne develops through a combination of changes involving oil production, dead skin cells, clogged hair follicles, the follicular microbiome and inflammation. Hormones, genetics and other individual factors can influence how susceptible your skin is to these changes.

In this dermatologist-written guide, we'll explain the major factors behind acne, how acne develops inside the pore, why acne can occur at different ages, common acne types, and what you can do to reduce breakouts.

In This Article

What Is Acne?

Acne is one of the most common skin conditions worldwide. It can affect teenagers, young adults and people well into adulthood.

Acne develops within hair follicles, which contain sebaceous glands that produce an oily substance called sebum.

When excess sebum and dead skin cells accumulate inside a follicle, the opening can become blocked. This can lead to blackheads and whiteheads. When inflammation develops deeper within the follicle, red pimples, pustules, nodules or cysts can occur.

How Acne Develops

Acne does not appear because of one single event. Several processes can interact inside the hair follicle.

Step 1: Excess Sebum Production

The sebaceous glands naturally produce sebum to help lubricate the skin.

When the glands produce excess sebum, the extra oil can contribute to congestion inside the hair follicle.

Step 2: Dead Skin Cell Build-Up

Skin cells are constantly shed and replaced. In acne-prone skin, dead skin cells can accumulate within the follicle and mix with sebum.

Step 3: Follicular Plugging

The combination of sebum and accumulated skin cells can form a plug inside the follicle.

If the opening remains closed, a whitehead can form. If the opening remains exposed to air, a blackhead can develop. The dark colour of a blackhead is not dirt; it results from changes within the material exposed to oxygen.

Step 4: Changes Within the Follicular Microbiome

The blocked follicle creates an environment in which Cutibacterium acnes, a bacterium normally found on healthy skin, can participate in inflammatory changes.

Acne is therefore not simply an infection caused by bacteria. Changes in the follicle, sebum, microbial environment and immune response all contribute to the development of acne.

Step 5: Inflammation

Inflammatory changes within the follicle can cause redness, swelling and tenderness.

Depending on how deep and inflamed the lesion becomes, this can result in papules, pustules, nodules or cyst-like lesions.

These processes explain why acne can appear in several different forms, from blackheads and whiteheads to deep, painful breakouts.

The 7 Most Common Factors Behind Acne

There is rarely one single explanation for acne. The following factors can increase susceptibility to breakouts or make existing acne harder to control.

1. Hormonal Changes

Hormones are an important influence on acne because they can affect sebaceous gland activity and oil production.

Hormonal fluctuations during puberty, menstrual cycles, pregnancy and other hormonal transitions may contribute to breakouts.

Conditions such as polycystic ovary syndrome (PCOS) may also be associated with persistent or hormonally influenced acne, particularly when other symptoms of hormonal imbalance are present.

If you experience recurring lower-face breakouts or acne that appears to follow a hormonal pattern, read our guide on Hormonal Acne: Causes, Symptoms and Treatment Options .

2. Excess Sebum Production

Sebum is the natural oil produced by the sebaceous glands.

People with oilier skin generally produce more sebum, and excess sebum can contribute to follicular congestion.

However, oily skin does not automatically mean that someone will develop acne. Genetics, hormones, inflammation and other factors also matter.

If you have oily, acne-prone skin, a consistent acne skincare routine for oily skin can help you manage congestion without over-stripping the skin.

3. Clogged Pores

Clogged pores are one of the central processes in acne development.

When excess oil and dead skin cells accumulate inside a follicle, they can form a comedone—the medical term for a clogged pore.

Blackheads and whiteheads are both types of comedones.

Ingredients such as salicylic acid can help exfoliate within the pore and reduce congestion over time.

Learn more in our guide: Salicylic Acid for Acne: Benefits, Side Effects and How to Use It .

4. Stress

Stress does not directly cause acne, but it may worsen existing breakouts in some people.

Stress can affect physiological processes, sleep patterns and everyday habits that may make acne harder to control.

For example, stressful periods may be accompanied by poor sleep, changes in skincare habits or increased touching and picking of the skin.

For a deeper explanation, read: Does Stress Cause Acne?

5. Genetics

Your genes can influence how likely you are to develop acne.

A family history of acne may affect factors such as sebum production, follicular behaviour and inflammatory responses.

If one or both parents experienced significant acne, you may have a higher susceptibility to developing it yourself.

Genetics cannot be changed, but understanding your susceptibility can help you focus on consistent prevention and treatment rather than blaming yourself for breakouts.

6. Skincare and Haircare Products

Certain skincare, makeup and haircare products may contribute to clogged pores in acne-prone individuals.

This can be particularly noticeable around areas such as the hairline and forehead when oily hair products come into contact with the skin.

When appropriate, look for products labelled:

• Non-comedogenic
• Oil-free
• Won't clog pores

However, a product being labelled non-comedogenic does not guarantee that it will suit every person's skin.

Haircare products can also contribute to small bumps and breakouts around the hairline and forehead in some people.

7. Lifestyle and Behavioural Factors

Some everyday habits can make acne harder to control or worsen existing inflammation.

These may include:

• Irregular or inadequate sleep
• High or persistent stress
• Frequently touching the face
• Picking or squeezing pimples
• Frequently changing skincare products
• Not cleansing the skin appropriately after heavy sweating

These factors are generally better understood as contributors or aggravating factors rather than standalone causes of acne.

What Causes Acne at Different Ages?

Teenage Acne

Hormonal changes during puberty are a major reason acne becomes common during the teenage years.

Increasing androgen activity can stimulate the sebaceous glands and increase sebum production, making clogged pores and inflammatory acne more likely.

Acne in College Students and Young Adults

Acne may continue into the late teens and twenties.

Changes in routine, stress, sleep patterns, skincare habits and hormonal factors may all influence breakouts during this stage.

A simple and consistent skincare routine for college students with acne can be easier to maintain than a complicated routine with multiple products.

Adult Acne

Adults can develop acne for the first time, or continue to experience acne that began during adolescence.

Adult acne may be influenced by hormonal fluctuations, genetics, stress and other individual factors.

Persistent adult acne, particularly when it follows a recurring hormonal pattern, may warrant a dermatological assessment.

Common Types of Acne

Acne can appear in several forms. Different types of lesions may also occur at the same time.

Whiteheads: Closed comedones that form when a pore becomes blocked and the opening remains closed.

Blackheads: Open comedones in which the material inside the pore darkens when exposed to air. The dark colour is not dirt.

Papules: Small, raised and inflamed red bumps that do not contain visible pus.

Pustules: Inflamed pimples containing visible pus.

Nodules: Large, deep and often painful inflammatory lesions.

Nodulocystic acne: Severe inflammatory acne involving deep nodules and cyst-like lesions that may increase the risk of scarring.

Deep, painful nodules or cyst-like lesions should be assessed by a dermatologist because early appropriate treatment can help reduce the risk of scarring.

Acne Myths You Should Stop Believing

Myth #1: Acne Is Caused by Dirty Skin

False.

Acne is not caused by poor hygiene. Scrubbing the skin aggressively can actually irritate it and make existing acne harder to manage.

Myth #2: Only Teenagers Get Acne

False.

Acne can persist into adulthood and can also begin for the first time in adults.

Myth #3: Popping Pimples Makes Them Heal Faster

False.

Picking and squeezing can increase inflammation, delay healing and increase the risk of post-acne marks and permanent scarring.

Myth #4: Acne Has One Single Cause

False.

Acne usually develops through several interacting biological and environmental factors.

Myth #5: Diet Is Always the Cause

False.

Diet may influence acne in some people, but it is not the universal cause of acne.

Learn more in our detailed guide: Can Diet Cause Acne?

How to Reduce Acne Breakouts

You cannot control every factor that contributes to acne, such as genetics or natural hormonal fluctuations.

However, you can control many of the habits that help support clearer-looking skin.

• Follow a consistent skincare routine.
• Use acne treatments suited to your skin and type of breakout.
• Choose non-comedogenic skincare, sunscreen and makeup where appropriate.
• Avoid aggressive scrubbing.
• Avoid picking or squeezing pimples.
• Cleanse gently after heavy sweating.
• Maintain healthy sleep and stress-management habits where possible.
• Give acne treatments enough time to work before constantly switching products.

Dermatologists generally recommend gentle skincare and patience because acne treatments often require several weeks of consistent use before meaningful improvement becomes noticeable.

Build a Routine Around Your Skin's Needs

Instead of choosing products based only on trends, build your routine around the type and severity of your acne.

For example, a basic acne routine may include:

• Gentle cleansing
• Appropriate acne treatment
• Lightweight moisturising
• Broad-spectrum sunscreen

If you have oily, acne-prone skin, explore our Acne Skincare Routine for Oily Skin .

When Should You See a Dermatologist?

Not every breakout requires a dermatologist, but professional assessment can be especially helpful when acne is persistent, painful or leaving marks.

Consider seeing a dermatologist if:

• Your acne is painful, deep or severe.
• You are developing nodules or cyst-like lesions.
• Acne is leaving dark marks or scars.
• Breakouts continue despite a consistent skincare routine.
• Over-the-counter treatment has not helped after an appropriate trial.
• You experience recurring hormonal-pattern acne.
• You suspect an underlying hormonal condition.
• Acne is affecting your confidence or quality of life.

A dermatologist can determine the type and severity of acne and recommend treatment appropriate for your individual skin.

Frequently Asked Questions

What is the main cause of acne?

There is no single cause of acne. Acne develops through a combination of excess sebum, follicular plugging, changes within the follicular microbiome and inflammation. Hormones, genetics and other factors can influence how susceptible someone is to acne.

Can oily skin cause acne?

Excess sebum can contribute to clogged pores and acne, but oily skin alone does not guarantee that someone will develop acne. Hormones, genetics, inflammation and other factors also play a role.

Can stress cause acne?

Stress does not directly cause acne, but it may worsen existing breakouts in some people. Stress can affect physiological processes, sleep and everyday habits that may make acne harder to control.

Read more: Does Stress Cause Acne?

Can hormones cause acne?

Hormonal fluctuations can influence sebum production and acne susceptibility. This is particularly common during puberty and can also occur during menstrual cycles and other hormonal transitions.

Can genetics cause acne?

Genetics can influence your likelihood of developing acne and may affect factors such as sebum production, follicular behaviour and inflammatory responses. A family history of acne can therefore increase susceptibility.

Does diet affect acne?

Diet may influence acne in some individuals. Research suggests that high-glycemic dietary patterns may worsen acne in some people, while some studies have also found an association between cow's milk and acne. Individual responses vary.

Read our detailed guide: Can Diet Cause Acne?

Can skincare products cause acne?

Some skincare, makeup and haircare products may contribute to clogged pores in acne-prone skin. Choosing appropriately formulated, non-comedogenic products may help reduce this risk.

How long does acne treatment take to work?

Many acne treatments require several weeks of consistent use before noticeable improvement. The timeline varies depending on the treatment, type and severity of acne. If your acne is not improving despite consistent treatment, consider consulting a dermatologist.

Can adults get acne?

Yes. Acne can persist from adolescence into adulthood or begin for the first time in adulthood. Hormonal fluctuations, genetics and other individual factors may contribute.

Does poor hygiene cause acne?

No. Acne is not caused by dirty skin. Excessive washing or aggressive scrubbing can irritate the skin and may make breakouts harder to manage.

Final Thoughts

Acne is rarely caused by one single factor.

It develops through a combination of excess sebum, follicular plugging, changes within the follicular environment and inflammation, with hormones, genetics, stress, products and other factors influencing individual susceptibility.

Understanding what is actually happening inside the pore is more useful than blaming one food, one product or one stressful day for every breakout.

The most practical approach is to identify the factors you can control, follow a consistent acne-friendly routine, avoid picking your skin and give appropriate treatment enough time to work.

If acne is painful, persistent, scarring or affecting your quality of life, professional assessment can help you understand the underlying factors and choose an appropriate treatment plan.

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About the Author

Dr. Nidhi Gupta
MD Dermatology

Dr. Nidhi Gupta is a dermatologist with a special interest in acne, pigmentation and evidence-based skincare. Through Aloe&Me educational content, she aims to simplify skincare science and help readers make informed decisions about their skin health.

Medical information on this page is intended for general education and does not replace personalised medical advice.