How cold sores develop
Cold cores, or fever blisters, are caused by a form of the herpes simplex virus (HSV-1 or HSV-2). The herpes virus causes a lifelong infection that can be dormant in your body for years before causing a cold sore to appear.
Although cold sores typically form on or in your mouth, they can also develop on your cheeks, nose, and eyes.
Once you’re exposed to the virus, something generally triggers the reoccurrence of sores. Possible triggers include:
- hormone fluctuations
- food allergies
- sun exposure
When cold sores do appear, they typically follow the same five stages:
Keep reading to learn what happens in each stage and how to find relief.
What do the cold sore stages look like?
Stage 1: Tingling
If you feel an unexplained tingling around your mouth, you may have a cold sore coming on. Tingling is usually one of the first signs that a cold sore is about to develop on the surface of the skin. The area may also burn or itch.
Treating a cold sore during the tingling phase may reduce its severity and duration, but it won’t prevent the sore from forming. Oral medication is most useful during this phase. The medication can also be used daily to prevent or limit outbreaks.
If you develop cold sores only every once in a while, you may find topical treatments beneficial. Some of these topical treatments include:
- doscosanol (Abreva), which is available over the counter (OTC)
- acyclovir (Zovirax), by prescription only
- penciclovir (Denavir), by prescription only
However, some research suggests these ointments can’t adequately reach the virus. So their effectiveness may be limited. A recent study shows that in the lab, aloe vera gel had virus-blocking activity against HSV. This may mean aloe vera may also be an effective topical treatment.
If you have frequent cold sores or would rather take oral medication, talk to your doctor. They may prescribe one of the following:
If this stage of the cold sore is painful or bothersome, you can take OTC pain relievers like acetaminophen (Tylenol) or ibuprofen (Advil). Creams with lidocaine or benzocaine may also provide relief.
Stage 2: Blistering
About a day or two after you feel the initial tingling phase, your cold sore will typically move to the blistering phase. This is when one or more blisters filled with clear fluid appear on the surface of the skin. The skin around and under the blisters will be red. The blisters may appear on your mouth or inside of it, including in your throat.
You may already be using a pain reliever, oral medication, or topical cream to alleviate the cold sore symptoms. In addition to these treatments, you should also increase your water intake. It’s important to stay hydrated especially when your mouth is sore.
Once cold sores appear on the surface of your skin, they can easily spread. Wash your hands with warm, soapy water after you touch the affected area, and avoid sharing food or drink during this time. Kissing and oral sex can also spread the virus, so use caution. You should limit intimate contact until the blisters are completely gone.
Blisters and the stages following them may cause discomfort during eating, as well. You should avoid certain foods, such as:
- spicy foods
- salty foods
- hot liquids
Stage 3: Weeping
The cold sore will break open, often within a few days of appearing on the surface of your skin. Open sores will be red and shallow. They are most contagious during this time.
If you haven’t already, consider using a topical or oral pain reliever to help ease your symptoms. You may also use a cold or warm compress.
Avoid picking at the sores. Picking can cause the condition to worsen or spread. It can also create a bacterial skin infection.
Stage 4: Crusting
After the weeping stage, your blister will dry. This begins the crusting stage. When the blister dries out, it will look yellow or brown. You should be careful to not aggravate the crusted blister.
Using cold and warm compresses and zinc oxide ointment may help at this stage.
Stage 5: Healing
The final stage of the cold sore is the healing stage. This is when the crusted blister scabs over. To keep the scab soft and to reduce irritation, try using emollients containing zinc oxide or aloe vera.
The scab will slowly disappear by flaking away. Cold sores generally don’t leave scars.
When to see a doctor
If you experience cold sores only on occasion, home treatment may be enough to minimize discomfort and speed up the healing process. But if you have regular cold sores, you should see your doctor for prescription medication. It may help limit the frequency and severity of your sores. Using lip balm with an added sunscreen is important as well.
You should also see your doctor if a cold sore:
- spreads to your eye
- is accompanied by a fever
- doesn’t clear within a week or two
- is surrounded by crusted or oozing skin
The bottom line
HSV is most contagious when cold sores are open and unhealed. However, the virus may also be contagious before or after the sores appear.
It’s best to take careful precautions when you experience cold sores:
- Avoid sharing utensils and hygiene products.
- Avoid physical contact with another person while the sores are present.
- Don’t share products you use to treat the cold sores.
- Wash your hands after treating a cold sore.