What Bacteria Causes Acne- And Is It Contagious?

If you’ve heard that bacteria play a role in causing acne, you may be worried about getting too close to someone with bad acne. After all, bacteria are contagious, and the last thing you want is to catch acne.

Luckily, acne is not contagious, and the bacteria that cause it can’t be transmitted, so you can safely get up close and personal to someone with acne without being at risk of catching it from them.

Read on to take a more in-depth look at the bacteria that cause acne and how they actually contribute to pimple formation.

What is acne?

Acne is caused when pores or hair follicles are blocked by sebum (the oil that your body naturally produces to lubricate your skin and hair), dead skin cells, and bacteria. The specific bacteria implicated in the pathogenesis of acne is Cutibacterium acnes. 

Acne is usually distributed over the face, jawline, neck, chest, and upper back, as those are the areas in which your sebaceous glands are densest. Sebaceous glands are the small glands at the base of the hair follicle that produce sebum. 

Anything that causes excessive sebum production, such as puberty, or that leads to an increased likelihood of pores becoming blocked, such as the use of occlusive skin products, can trigger acne. 

All you need to know about cutibacterium acnes

Cutibacterium acnes (C. acnes) is the bacteria that is most strongly linked to causing acne. It was previously called propionibacterium acnes.¹

C. acnes is a generally harmless, slow-growing, aerotolerant (meaning that it can survive in the presence of oxygen), anaerobic (meaning that it thrives in environments without oxygen), gram-positive bacteria. 

C. acnes is a commensal on the skin. This means that it normally lives on your skin under healthy conditions and doesn’t do harm or cause disease. In fact, the presence of C. acnes, along with certain other commensal skin bacteria, ensures that your skin remains healthy. 

C. acnes is critical in maintaining skin homeostasis and preventing harmful organisms from setting up home on your skin. Unfortunately, it is also involved in causing acne in certain environments, typically in the presence of excessive sebum. Because C. acnes is a commensal on your skin, it doesn’t jump from person to person transmitting disease. 

How does c. acnes cause acne?

The role of C. acnes in causing acne is very complex and likely involves multiple pathological processes and contributing factors.¹

Disruption of the normal skin microbiota can lead to overgrowth of certain strains of C. acnes that are more likely to cause acne. 

When a pore becomes blocked with a plug of dead skin cells and sebum, it creates a favorable environment for C. acnes to thrive. The bacteria proliferate and begin to irritate the lining of the pore or hair follicle, causing redness and inflammation. 

Whiteheads and papules in which C. acnes has proliferated can turn into deeper or larger pustules and cysts. 

Could it be another skin disorder?

Acne is not contagious, and C. acnes doesn’t transmit disease. Additionally, not all pimple-like lesions are necessarily acne. There are skin lesions that may have a similar appearance to acne that are contagious. 

A useful tip to suggest that your pimple-like lesions aren't true acne is if they appear over an extensive area in a very short period of time. Likewise, if you suddenly develop a pimple-like rash on previously clear skin and someone close to you had a similar rash a few days before, it’s unlikely that your pimples are acne. 

If you develop acne-like lesions over a short period of time or if you have any doubt that your skin disorder is, in fact, acne, it’s best to make an appointment to see your doctor for an accurate diagnosis. The treatment you require for your rash may be very different from the treatment used for acne. 

Acne treatments

There is a wide range of treatment options for acne, and it’s best to discuss these with your healthcare provider to see which is the most suitable for you. Several acne treatments specifically target the proliferation of C. acnes. 

Benzoyl peroxide is a topical treatment that can kill C. acnes. It is often used in conjunction with topical tretinoin, which helps to remove dead skin cells and unblock pores to make C. acnes more vulnerable to treatment. 

Commonly prescribed topical antibiotics include clindamycin and erythromycin. Topical antibiotics are usually only effective for mild acne.

For moderate to severe acne, oral antibiotics may be required. Typical oral antibiotics used in the treatment of acne are doxycycline, erythromycin, tetracycline, and trimethoprim/sulfamethoxazole. Oral antibiotics may be used in conjunction with topical tretinoin. Usually, it takes about three months for antibiotics to take full effect. It’s not recommended that you remain on antibiotic treatment long-term due to the risk of developing antibiotic resistance. 

The lowdown

Although bacteria partially cause acne, it is not contagious. The bacteria responsible for causing acne is Cutibactrium acnes. 

It’s likely that disruption of the normal skin flora contributes to the overgrowth of C. acnes, leading to the development of acne. 

Although acne is not contagious, there are skin conditions that can mimic acne that may be contagious. See your doctor if you are unsure of your diagnosis. Acne can be treated. Some acne treatments, such as topical antibiotics, topical benzoyl peroxide, and oral antibiotics, specifically target the proliferation of C. acnes.