Can antibiotics prevent cellulitis from coming back?

Photo of an elderly man taking antibiotics (PantherMedia / Kasia Bialasiewicz)

People who have already had cellulitis can prevent it from returning by taking low-dose penicillin. When used for this purpose, the penicillin is taken every day for up to twelve months. This preventive treatment is safe and well tolerated.

Cellulitis is a bacterial skin infection that can arise if bacteria get into injured skin, cracked skin or a sore and infect the deeper layers of skin. It can usually be treated successfully with antibiotics.

Some people get cellulitis again and again. This is thought to happen in about one third of all people who have had cellulitis. Doctors will try to find the cause of the new infection and treat it. Possible causes include skin conditions like athlete's foot or impetigo, as well as poorly controlled diabetes.

If treating the cause doesn't help stop cellulitis from returning, preventive treatment with antibiotics can help. This involves taking antibiotics twice a day over a long time period. Alternatively, the antibiotics can be injected into a muscle every 14 days.

Research on preventive treatment with penicillin

Various groups of researchers have looked into the possible advantages and disadvantages of preventive treatment with antibiotics in people who keep getting erysipelas or cellulitis infections. The researchers found five studies with a total of about 500 patients.

Two of the five studies were particularly conclusive because quite a lot of people took part in them and they were designed and carried out well. Both of the studies also kept in touch with the participants for three years to see whether the skin infection returned. This meant that they were able to provide information about how well the antibiotics worked in the long term.

In one study, the participants had cellulitis for the first time. They were randomly assigned to two groups. One group was given penicillin for six months, and the other was given a placebo (fake drug) for six months. The dose of penicillin taken was 500 mg per day (two 250 mg tablets), which is quite a small dose. In the other study, participants had to have had cellulitis at least twice already. The treatment was the same as in the first study, but lasted twelve months instead.

Antibiotics lower the risk of further infections

When analyzed together, the results of these two studies showed that taking penicillin over a long period of time prevents further infections. During the three years in which the researchers stayed in touch with the study participants,

  • 43 out of 100 people who were given the placebo developed a new bacterial skin infection.
  • 32 out of 100 people who were given penicillin developed a new bacterial skin infection.

In other words, penicillin prevented 11 out of 100 people from getting another infection during this time period.

Low-dose penicillin is well tolerated

Both studies also looked into how common side effects were. The researchers were especially interested in nausea, diarrhea, rashes and fungal infections because these side effects are often associated with antibiotics.

The results showed that these side effects weren't more common in the penicillin group than they were in the placebo group. So, if people take penicillin and have diarrhea, for instance, it doesn't necessarily mean that the diarrhea was a side effect of the medication.

The reason why the antibiotics were so well tolerated in the studies might be because they were taken in such small doses. But even low-dose antibiotics might still cause side effects sometimes. Although a few hundred people took part in the studies, the total number of participants isn't enough to draw conclusions about rare side effects.

Some people aren't able to take penicillin at all because they are allergic to it – but this is very uncommon. If you take antibiotics, it's always a good idea to find out how to use them properly. The incorrect use of antibiotics can make bacteria become resistant to these drugs, and then they no longer work properly.