Herpes simplex one often causes cold sores on the lips and around the mouth area. HSV-1 remains dormant until it’s triggered, but flare-ups only occur once or twice a year for most people. When they do happen, they can be particularly unpleasant and painful.

Typically, fever blisters will heal naturally in under two weeks. Unfortunately, open sores can become infected by bacteria, often through your own careless touch. Knowing how to heal an infected cold sore is vital if you want to reduce the pain and shorten the recovery time.

Think of an infected cold sore as you would any other infected wound. If you cut your hand, for example, you have to treat the infection. Cold sores that are infected can sometimes lead to more severe health issues, such as impetigo. This is a contagious bacterial skin infection.

So, healing the infection should be your priority. In this guide, we’re going to dive deeper into how to tell if you do have an infection. We’ll explain how to heal the area faster and enjoy instant relief from the discomfort.

Cold Sore vs. Bacterial Infection

Cold sores are the visual and physical byproduct of the herpes simplex virus. While these blisters can be annoying and painful, the existence of a sore is normal if you have HSV-1.

Although caused by a virus, having a fever blister does NOT mean you have an infection. While the terminology has become interchangeable, there is a significant difference between having a cold sore and an infected open fever blister.

When a cold sore is interrupted by an external factor, it can become infected. This is known as a bacterial infection. Just like most any type of flesh wound, bacteria can invade the area, leading to infection and delayed healing.

To summarize:

  • A fever blister is not a sign of infection, but rather the byproduct of being an HSV-1 carrier. While it is common to refer to a cold sore outbreak as an infection, they aren’t actually infected at that stage.
  • Cold sores are flesh wounds. While they are the result of an incurable virus, the visual sores are perfectly normal. Similar to any other cut or abrasion to the skin, bacteria can invade the area. When this occurs, an infection can develop.[1]

How Do Cold Sores Become Infected?

Cold sores can become infected through neglect, touch, and ‘inappropriate’ alternative treatments. In many cases, bacterial infection is the result of improper care or touching the lesion with your fingers. The touching, poking, picking, and pulling off a sore (or scab) can introduce bacteria.

The early removal of a blister scab can also lead to infection. Fully exposed, the visible ulcer can become susceptible to various particles and debris. Most of these will have come from your own infected fingers. While a cold sore infection can happen, it isn’t really that common.

How Do I Tell if a Cold Sore is Infected with Bacteria?

The main symptoms of a bacterial infection are discoloration, swelling, slower healing, and appearance of pus in the blister. There will be noticeable changes to the lifecycle.

Without treatment, most outbreaks will last for under two weeks and go through the five cold sore stages. The lengthening of a particular stage and/or the extended duration of the outbreak can be a sign of trouble.

When a cold sore becomes infected, it isn’t uncommon for the area around the blister to swell and turn a reddish color. It’s not uncommon for the blister to linger. Cold sores that seemingly refuse to burst can be a symptom of infection.

To summarize:

  • Although symptoms of an infected sore will vary from person-to-person, general swelling and inflammation is a universal sign. Discoloration at the location site, along with improper healing, are also red flags.
  • Fever blisters that refuse to pop can also be a sign of trouble. If your outbreak has carried on for almost a month, then something is wrong.
  • Many bacterial infections are introduced by the individual. For example, you’ve used a sharp object to burst your cold sore.

What Happens When a Fever Blister Becomes Infected?

When a fever blister becomes infected, the healing process will cease. While swelling and discomfort are common, the more significant concern is the increased amount of time that it takes to recover.

Although rare, a bacterial infection could introduce a condition known as impetigo. Hallmarked by rash and blisters, impetigo is a highly contagious skin infection.[2] If a cold sore becomes infected, it could co-exist with the rash and blisters that are associated with impetigo.

Because both HSV-1 and impetigo can spread and be transferred to others, these conditions are severe.

Is an Infected Cold Sore Dangerous?

In most cases, a cold sore infection is more painful than dangerous. Because cold sores are naturally contagious, the only real risks are viral spreading and improper healing. It may extend your period of recovery, but it should not normally be viewed as dangerous.

If you are experiencing pain, discoloration, prolonged healing, etc., we encourage you to let your physician have the final word.

How Can Pain, Redness, and Swelling Be Reduced?

The pain, redness, and swelling that is common with an infected fever blister can be reduced. In the same way that you would attempt to eliminate specific symptoms of a “normal” cold sore, you can do the same with an infected cluster.

While various treatment methods are important, certain personal decisions can also help to alleviate your discomfort. The act of covering up your cold sore from multiple irritants is almost as worthy as an active remedy.

Noted below are several keys to feeling better and helping your infected sore heal.

Do Not Touch the Sore

One of the best ways to decrease the symptoms associated with an infected cold sore is to take the hands-off approach. In the same way that it is ill-advised to touch a cold sore, you should do the same with an infected blister.

Although it is human nature to check things out, doing so can cause more harm than good. If your cold sore has become infected the best thing you can do is treat it and let it heal. Touching your sore could be how it became infected in the first place.

Why is my cold sore infected and swollen?

Use a Cold Compress (or Ice)

The use of a cold compress or ice can numb the pain and swelling of an infected sore. Serving the same purpose as when applied to a routine outbreak, ice or a compress can provide fast relief. Although it won’t cure the infection, it will help you deal with the overall problem.

Always be gentle with this form of application. Never apply harsh pressure to the sore but rather just allow the ice or compress to rest on the blister gently. Keep it on for a few seconds. Remove when it gets too cold and then re-apply.

If your sore is still in the blister stage and has additional swelling due to the infection, you should be extra cautious. In this case, it might be wise to apply a small compress. You can purchase cold gel packs that are only a few inches wide. This type of pack is good for an infected sore as it will allow you to control the pressure with more direction. The smaller the compress, the easier it is to handle.

Avoid Irritating Foods and Beverages

In the same way that specific triggers should be avoided, the same rules apply when you have active cold sores. If you have an infected blister, you should always be mindful of your food and drink selections. You should avoid acidic and spicy foods, in particular.

The primary concern with trigger foods and beverages is lip contact. When you drink and eat (in a normal setting) the food or liquid will inevitably come in contact with your lips. Perhaps even rest on your lips for a brief moment. If the drink or food choice is harsh, it could contaminate your infected sore even more. For example, orange juice (which is rich in citric acid) coming into contact with your infected blister.

While avoiding acidic and spicy menu items is the key, attempting new methods of consumption could also be a plan. If you are concerned about food particles touching your sore, try placing the food directly into your mouth rather without it touching your swollen lips.

Pain Relievers

The use of anti-inflammatory medications can provide pain relief if your infected blister cluster has become too painful.[3] Taking Ibuprofen can help to reduce your pain and alleviate the symptoms, such as swelling.

While Ibuprofen can be quite harsh if abused, this medication can come in handy. Use Ibuprofen in tandem with ice or a cold compress.

General points of note:

  • Ibuprofen should be taken every 4-6 hours with a full glass of water.
  • Do not take this drug lying down or lie down for at least 10-20 minutes after consumption.
  • While this drug can be taken on an empty stomach, it is best to consume with a meal.
  • Do not take Ibuprofen for more than ten consecutive days unless directed by your physician.

How Can an Infection Be Treated Safely?

Always remember that a cold sore is a flesh wound. It is not uncommon for skin wounds to become infected with germs and bacteria. Infected fever blisters, just like routine cold sores, can be treated safely at home. It all comes down to the right treatment and taking appropriate precautions.

Your doctor may prescribe a treatment to clear up the infection. For example, impetigo can be eliminated with a topical ointment, such as Mupirocin. If your infection is really severe, you may be prescribed an antibiotics, such as penicillin or cephalosporin.

Will an Over-The-Counter Treatment Work?

Unless your infection involves impetigo or some other form of growing and spreading bacteria, an OTC antibacterial cream should be used in conjunction with your preferred cold sore treatment. One of the most popular choices for self-medication is Neosporin.

Bacteria has infected my fever blister

Should I see a Doctor?

A lack of healing, the location, and the severity should all be carefully considered before consulting your physician.

Listed below are examples of occasions where you should visit your doctor:

  • If you have applied medication for more than two weeks, but the area is NOT healing. This is essential if it worsening.
  • Not every outbreak is located directly on the lip. Some outbreaks are in one corner of the mouth, right above the lip border, and even on the chin area. It may be that the location of your outbreak (infection) that is the problem. For example, you’re finding it really difficult to eat food.
  • If you are experiencing severe pain, skin discoloration, bleeding, etc., you should seek medical attention. Infection symptoms can occur outside of the problem region. If you’re experiencing headaches, fever, fatigue, nausea, swollen lymph nodes etc. you should urgently seek medical assistance.

How Long Will It Take for a Bacterial Infection to Go Away?

The duration of a bacterial infection largely depends on the severity of the infection.

If it has resulted in impetigo, for example, the recovery process will take much longer. Starting a treatment without delay will expedite the healing process. Unless you get rid of the infection, the area will remain red and swollen.

Just treat the infection with the right over-the-counter or prescription medication and look out for any visual signs of recovery. Don’t create a mental timetable for your recovery. You will only feel frustrated when the blister hasn’t healed in line with your personal timeline.

How Do I Prevent Infection in the Future?

Although infected cold sores can occur, they are uncommon. Most infections have an external cause, such as touching the lesion with dirty and bacteria-riddled fingers. That’s one of the reasons why you should always wash your hands and avoid touching the site of a cold sore.

The best way to prevent an infection is to treat your fever blisters with FDA-approved medications. Guard your open blisters against particles and debris with a Compeed invisible patch. This will not only treat the area but shield it from potential bacteria.

One way to avoid a prolonged outbreak and eliminate infection is Virulite cold sore device. Courtesy of light technology the Virulite device will reduce the duration of your outbreak without any messy creams and ointments. Healing has been known to take place in as little as three days.

The best way to prevent a cold sore infection is by strengthening your immune system. Your body will be better placed to fight off the herpes virus, and you’ll recover quicker if you do get a cold sore infection.


  1. Babamahmoodi F, Alikhani A, Ahangarkani F, Delavarian L, Barani H, Babamahmoodi A. Clinical Manifestations of Herpes Zoster, Its Comorbidities, and Its Complications in North of Iran from 2007 to 2013. Neurology Research International. 2015;2015:896098. doi:10.1155/2015/896098.
  2. Nardi NM, Schaefer TJ. Impetigo. [Updated 2017 Apr 21]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2018 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK430974/
  3. Al-Ghazawi FM, Ramien ML, Brassard A, Shear NH, Beecker J. Management of Pain Associated with Selected Conditions in Dermatology. Am J Clin Dermatol. 2016 Oct;17(5):463-474.