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Doxycycline: What it is, How it Works, Side Effects & More

Kristin Hall

Medically reviewed by Kristin Hall, FNP

Written by Our Editorial Team

Last updated 8/10/2022

Doxycycline is an antibiotic that’s used to treat a variety of different conditions, including moderate to severe inflammatory and non-inflammatory acne. 

If you have acne, your healthcare provider may have recommended doxycycline as a treatment. Doxycycline may also be prescribed if you have a bacterial infection, such as a skin infection, dental infection, eye infection or sexually transmitted infection. 

When used as prescribed, doxycycline can get rid of the bacteria that cause acne. 

Below, we’ve explained what doxycycline is and how it works, both as a treatment for a range of infections and as an anti-acne medication. We’ve also listed side effects, interactions and other key information about doxycycline that you should know before using this medication.

What is Doxycycline?

Doxycycline is a type of prescription antibiotic referred to as a tetracycline. It’s sold as a tablet, capsule and liquid solution, and is prescribed to treat a diverse range of bacterial infections and conditions caused by bacteria. 

Doxycycline is also sometimes prescribed as a traveler’s medication to prevent diseases such as malaria

Due to its diverse range of applications, doxycycline is a very common medication. Millions of people use doxycycline in the U.S. every year. 

How Doxycycline Works

Doxycycline works by killing or slowing down the growth of certain types of bacteria, including the types of bacteria responsible for acne and other diseases and conditions.

More specifically, doxycycline stops bacteria from producing certain proteins that are essential for their growth and development. This prevents the bacteria from replicating, essentially killing off the bacteria or controlling the severity of a bacterial infection.

How Doxycycline Works as an Acne Treatment

As an acne treatment, doxycycline works by killing off the bacteria that can contribute to acne.

Acne develops when sebum, dead skin cells and other particles block the hair follicles, creating whiteheads, blackheads and other pimples. Sebum, a key cause of acne, is often produced due to fluctuations in your hormones — a topic we’ve covered in our guide to hormonal acne

Not all acne becomes inflamed. However, when bacteria becomes trapped inside a blocked hair follicle, it can develop into an infection that causes a painful, irritated and swollen acne lesion to form. 

The bacteria responsible for these infected, inflamed pimples is known as cutibacterium acnes, or simply C. acnesformerly known as propionibacterium or P. acnes

  1. acnes bacteria live within your pores and hair follicles, as well as on the surface layer of your skin. They feed on your skin byproducts and sebum, using the nutrients produced by your body to replicate and spread. 

When C. acnes bacteria become trapped inside a blocked follicle, they multiply rapidly, causing the acne lesion to become inflamed, swollen and painful. 

Research into the C. acnes bacteria has found that it’s highly sensitive to cycline antibiotics — the class of medications to which doxycycline belongs.

As an antibiotic, doxycycline works by killing the C. acnes bacteria. Over the long term, this can help to reduce the severity of acne breakouts and prevent new acne from developing. 

Doxycycline has been used for decades as an effective acne treatment, with one early study from 1970 finding that daily use of doxycycline reduces inflammatory acne in 33 percent of adults after four weeks of use.

Newer studies have produced similar findings. In one study from 2003, researchers gave either doxycycline or a non-therapeutic placebo to a group of 51 adults with moderate facial acne over a period of six months. 

The researchers found that twice daily use of doxycycline “significantly reduced” the number of acne lesions, all with no detectable antimicrobial effects on the skin of the participants. 

A separate scientific article from 2006 noted that antibiotics like doxycycline are “significantly more effective” than placebo as treatments for acne — especially if used as part of a combination treatment.

Like many other acne treatments, doxycycline may not produce immediate improvements. It may take several weeks for you to notice a reduction in acne lesions after taking doxycycline, and several months before you experience significant improvements.

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Doxycycline Dosages

Doxycycline is prescribed to treat a large variety of conditions at a range of different dosages. 

For treating acne, a typical starting dosage of doxycycline is 100mg to 200mg per day. Depending on the severity of your acne and your response to the medication, your healthcare provider may adjust your doxycycline dosage over time. It’s also worth noting that doxycycline is typically meant for short-term use — three to four months — and is not considered a long-term treatment.

For other conditions, doxycycline may be prescribed at a different dosage. Carefully follow the instructions provided by your healthcare provider or pharmacist and use this medication only as prescribed. 

Doxycycline Side Effects and Interactions

Doxycycline can cause side effects. The most common side effects of doxycycline are nausea, headaches, which affect between 10 and 25 percent of people who use doxycycline. Other common side effects include:

  • Abdominal pain and distention

  • Acid indigestion

  • Anaphylactic reaction

  • Anxiety

  • Back pain/back ache

  • Bacterial vaginitis

  • Bronchitis

  • Coughing

  • Diarrhea

  • Dry mouth

  • Dyspepsia (indigestion)

  • Hypertension

  • Increased AST levels

  • Increased blood glucose

  • Increased LDH

  • Influenza

  • Joint pain

  • Menstrual cramps

  • Nasal congestion

  • Nasopharyngitis

  • Periodontal abscess

  • Pharyngolaryngeal pain

  • Photosensitivity dermatitis

  • Rash

  • Sinus congestion

  • Sinus headaches

  • Sinusitis

  • Sore throat

  • Stomach discomfort

  • Tooth disorder

  • Upper abdominal pain

  • Vomiting

  • Vulvovaginitis

Not everyone who uses doxycycline will experience side effects. Side effects from doxycycline may be mild and temporary. If you experience side effects that don’t go away over time, talk to your healthcare provider.

Although uncommon, doxycycline may cause serious side effects, including headaches, blurry vision and vision loss due to elevated blood pressure in the skull. 

Other serious potential side effects include painful irritation of the esophagus; severe, ongoing diarrhea; anemia and severe skin reactions. 

If you experience any serious side effects from doxycycline, contact your healthcare provider or healthcare professional. If you experience severe side effects that you think may be life-threatening, call 911 for emergency assistance. 

Doxycycline and Sun Sensitivity

Doxycycline may cause your skin to become more sensitive to sunlight. You may experience rashes, itchiness, redness or become more sunburned than normal while using doxycycline, even after you spend a short amount of time outside in the sunlight.

To reduce your risk of developing sunburn or a skin rash, avoid spending too much time out in the sun after you start using doxycycline. You should also:

  • Use an SPF 15 or stronger sunscreen before you go outside, especially if it’s a sunny day. It’s also important to protect your eyes by wearing a pair of sunglasses that offer total or near-total UVA and UVB protection.

  • Given the effect of doxycycline on the skin (it has been shown to increase skin sensitivity to the Sun's UV rays), it may help to apply a sun-protectant lipstick or balm before going out.

  • Avoid going outside for long periods of time during the peak sunshine hours (10 a.m. to  3 p.m.). You can check the UV index online for your region to see when the sun is most likely to irritate and burn your skin.

  • Avoid tanning beds and other unnatural sources of UV exposure, as these can damage and irritate your skin.

If you’re prescribed doxycycline, your skin may become more sensitive to sunlight over time. It’s best to talk to your healthcare provider if you experience any skin-related issues, such as sunburn, itching or irritation, while using doxycycline. 

Interactions Between Doxycycline and Other Medications

Doxycycline can interact with other medications, including over-the-counter medications, health supplements and herbal products. Some of these interactions can potentially cause dangerous side effects, while others may make doxycycline more or less effective.

You should not use doxycycline with isotretinoin.. Used together, these medications may increase your risk of experiencing intracranial hypertension, a potentially serious condition that can cause permanent vision loss. Doxycycline should also not be used with penicillin. 

Other medications that can interact with doxycycline include anti-seizure medications, such as certain barbiturates, anti-epileptic medications such as phenytoin and anticonvulsants such as carbamazepine. Doxycycline may also interact with warfarin and certain antacids.

To avoid interactions, inform your healthcare provider of all other medications you use or have recently used before using doxycycline. Our full guide to doxycycline interactions goes into more detail on the drug and food interactions you should be aware of before using doxycycline. 

Doxycycline Food Interactions

Doxycycline may interact with foods that contain calcium, causing less of this medication to be absorbed by your body. If you often eat high-calcium foods such as milk, cheese or yogurt, it’s best to avoid these foods for one hour before and after taking doxycycline. 

However, some people who take doxycycline hyclate may experience gastrointestinal irritation. If this is the case, you can take your medication with a glass of milk.

Doxycycline and Pregnancy

There is very little research on the effects of doxycycline during pregnancy. Doxycycline has an FDA category D rating, indicating that there is positive evidence of some risk to the fetus if this medication is used during pregnancy.

If you’re prescribed doxycycline to treat acne or any other health condition and believe you may be pregnant, talk to your healthcare provider. You should also talk to your healthcare provider if you’re planning to become pregnant in the near future and currently use doxycycline. 

Doxycycline can pass into breast milk and may cause side effects in infants. If you breastfeed your children, talk to your healthcare provider before using doxycycline. 

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Learn More About Treating Acne

Dealing with acne can be a frustrating, stressful process. From the occasional breakout before or during your period to stubborn, painful acne, few things are as irritating as trying to get rid of acne that just refuses to disappear.

Doxycycline is one of several medications used to treat and prevent acne. Depending on your type of acne and the severity of your breakouts, your healthcare provider might prescribe it on its own or as one of several medications and skincare products. 

Our guide to the most effective acne treatments goes into more detail about other options that are available for clearing up your skin and getting rid of acne for good, from facial washes and creams to birth control and more. 

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment. Learn more about our editorial standards here.