Cephalexin, also spelled cefalexin, is an antibiotic. It belongs to a class of antibiotics known as first-generation cephalosporins, which doctors use to treat a range of bacterial infections.

Cephalexin is an antibiotic that a doctor may prescribe to treat various infections, including those of the skin, middle ear, upper respiratory tract, and urinary tract. It is part of the World Health Organization’s (WHO) List of Essential Medicines, meaning experts consider it a necessary medication for a basic healthcare system.

There is a common misconception that using alcohol with antibiotics can cause side effects or decrease their effects. However, the evidence supporting this notion is not robust. That said, while cephalexin does not directly interact with alcohol, some people may wish to avoid drinking while undergoing antibiotic treatment for various reasons.

Keep reading to learn more about the effect that alcohol can have on people taking cephalexin.

Although it is not the case with some other antibiotics, cephalexin and alcohol are safe to consume together. However, some people report unpleasant side effects.

The side effects of cephalexin can include nausea and indigestion. Some people can experience these effects with alcohol and may find that combining the two may worsen them.

Many individuals believe that consuming alcohol while taking antibiotics can be dangerous. Although this is true for some types of antibiotics, such as metronidazole and tinidazole, it is not for cephalexin.

Additionally, some people may avoid alcohol while taking antibiotics because they fear that alcohol can render the medication ineffective. Generally, this is not the case. However, alcohol may reduce the effectiveness of some antibiotics, such as doxycycline.

Additionally, those with a history of chronic alcohol consumption or liver problems should not use this type of medication.

As with other cephalosporins, the most common side effects of cephalexin are gastrointestinal problems, including:

Some less common side effects of cephalexin include:

Allergic reactions

Researchers estimate that 1.3% to 1.7% of people in the United States develop allergic reactions to cephalosporins. Additionally, the risk may be higher for those allergic to penicillin.

A person can also develop an allergy to cephalexin if they have taken penicillin previously. It happens when someone takes penicillin and their immune system generates IgG and IgM antibodies. These antibodies can bind to cephalexin once a person takes it orally.

Common symptoms of an allergic reaction include:

In rare cases, a person may experience an extreme allergic reaction known as anaphylaxis. This is a potentially life threatening condition that requires urgent medical attention.

Anaphylaxis is a severe allergic reaction that can be life threatening. The symptoms develop suddenly and include:

  • hives
  • swelling of the face or mouth
  • wheezing
  • fast, shallow breathing
  • a fast heart rate
  • clammy skin
  • anxiety or confusion
  • dizziness
  • vomiting
  • blue or white lips
  • fainting or loss of consciousness

If someone has these symptoms:

  1. Check whether they are carrying an epinephrine pen. If they are, follow the instructions on the side of the pen to use it.
  2. Dial 911 or the number of the nearest emergency department.
  3. Lay the person down from a standing position. If they have vomited, turn them onto their side.
  4. Stay with them until the emergency services arrive.

Some people may need more than one epinephrine injection. If the symptoms do not improve in 5–15 minutes, or they come back, use a second pen if the person has one.

Cephalexin is a common antibiotic that doctors prescribe for a range of bacterial infections. However, doctors can provide alternative antibiotics to treat people who are hypersensitive to cephalexin and other first-generation cephalosporins.

Individuals with a known allergy to penicillin are less likely to experience an allergic reaction to newer third- or fourth-generation cephalosporins, such as:

  • cefepime (Maxipime)
  • ceftolozane-tazobactam (Zerbaxa)
  • ceftazidime (Fortaz)
  • ceftriaxone (Rocephin)

If a person has a fungal skin infection, their doctor may prescribe griseofulvin as an alternative to cephalexin.

Griseofulvin is an oral medication that helps treat fungal infections of the skin, nails, and hair follicles.

It can be effective against dermatophytes, a type of fungus. They can cause infections such as:

However, it is ineffective against species of Candida, so it will not treat yeast infections. A person may need to use the medication for several weeks or months before the infection clears.

Overall, griseofulvin causes few side effects. However, some people may experience gastrointestinal problems, such as:

  • nausea
  • vomiting
  • diarrhea
  • headaches
  • allergic reactions

People may need to limit or avoid consuming alcohol with isoniazid and linezolid antibiotics.

Isoniazid is an oral antibiotic that doctors may prescribe to treat tuberculosis, a serious infection affecting the lungs. Isoniazid works by killing the bacteria that cause the condition.

However, this medication can cause severe and life threatening liver damage. Therefore, a doctor may not prescribe isoniazid for anyone with liver problems. People with a history of alcohol misuse are also at increased risk for developing liver damage while taking isoniazid. Avoiding alcohol while taking this drug may be a precautionary measure that individuals should take.

Linezolid is an oral antibiotic that belongs to a class of medications called oxazolidinones. Doctors may prescribe it for infections, such as pneumonia and skin infections.

People should also avoid large amounts of an amino acid called tyramine while taking linezolid, as it may lead to sudden changes in blood pressure. Tyramine is present in certain foods and beverages containing alcohol, such as draft beer and red wine.

Learn more about antibiotics and alcohol.

Although cephalexin and alcohol are safe to use in combination, people taking the antibiotic for an active urinary tract infection (UTI) may still benefit from avoiding alcohol altogether.

Doctors usually advise people with UTIs to drink more water in an attempt to “flush out” the infection. Drinking alcohol tends to dehydrate the body and may prolong bladder irritation.

Effects of alcohol on the immune system

Drinking alcohol while experiencing a UTI increases the strain on the liver, which is already working to overcome the infection.

Alcohol may also disrupt the immune system by disturbing sleep patterns and causing gastrointestinal symptoms.

Each of these effects can impair the ability of the body to recover from infection, possibly prolonging recovery.

While consuming alcohol in moderation when taking cephalexin is safe, the two substances can cause similar side effects. Taking them in combination may worsen these side effects.

For people with an active UTI, alcohol may increase further irritation and potentially extend recovery time.

In general, moderate alcohol intake will not affect cephalexin’s effectiveness. However, it is usually best for a person who is feeling unwell to abstain from alcohol or limit their intake to allow their body to rest.