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Knowing if you have a cold sore or a pimple is important to help you select the appropriate treatment. If treated like a pimple, you could risk spreading a cold sore — whereas a harmless pimple along the lip line should give you no cause for alarm.
However, differentiating between a cold sore and a pimple can be extremely difficult, especially when the sore is first developing. Early cold sores and pimples often appear nearly identical, and it can take time for any differences to become obvious, making it challenging to tell them apart.
Determining between a cold sore vs. a pimple on your lip is much easier when you learn the fundamental differences between pimples and cold sores. Learning about their causes, where they occur, and how they progress will help you identify them and handle them more effectively.
To understand the causes of cold sores and pimples, it's necessary to learn what exactly they are. Knowing why they occur will help you determine possibilities according to your symptoms.
Cold sores are caused by the herpes simplex virus, which sometimes creates outbreaks of small ulcers on or around the lips.
Not all mouth ulcers are cold sores, but it is probably herpes if the sores appear on the outside of the mouth. Canker sores are another type of mouth ulcer, but they only occur on the inside of the mouth.
Note that it's possible for cold sores to appear on the inside of the mouth as well, although that is less common than on or around the lips.
A cold sore is more likely to develop during times of sickness or stress, especially if you’re experiencing:
Colds, fevers, or the flu
Too much exposure to sunlight
Cuts or other traumas to the face, including surgery
Cold sores usually last between 7–10 days. They are highly contagious and can spread to other parts of the body, as well as to other people.
Pimples occur when a pore becomes clogged by dead cells and oils, which allows bacteria to multiply and cause a small round swelling under the skin. They can be totally painless or quite uncomfortable.
Pimples are not contagious, and though they often disappear on their own, they can last for several weeks or longer depending on how deep the infection is and other factors.
Another cause of pimples is acne, a skin condition that causes recurring pimples.
Differentiating between cold sores and pimples early on is important because, unlike pimples, cold sores are contagious. Cold sores and pimples may seem like infected ingrown hairs at first, and even when they get slightly larger, they can both look like pimples. However, this is only true if an infected ingrown hair causes pustules to form.
Eliminating the possibility of an infected ingrown hair is important, so precautions can be taken to prevent a potential cold sore from spreading and enlarging.
The location of the sore may be sufficient to identify a cold sore or pimple. Generally, pimples only occur outside or at the lip line, not on the lip itself. Cold sores can occur anywhere on or around the lip. If a pimple-like sore occurs on the lip, it is most likely a cold sore, not a pimple. If it occurs on the face around the lip, it could be either.
They also differ by sensation and the way that they progress over time. With cold sores, there are a variety of other possible symptoms that could occur simultaneously, which can help to determine that it's a cold sore.
Complicating the matter is that cold sores can also occur on the chin or neck — but over time, the visible difference between cold sores and pimples becomes clearer. It's even possible for cold sores to progress from small pimple-sized sores to blisters in a matter of hours. Also, cold sores often occur in clusters, which can merge into a large blister.
Those blisters can then erupt, oozing a highly contagious clear liquid that crusts over once dry.
If the sore changes rapidly, it is most likely a cold sore, not a pimple. Cold sores can be verified conclusively through a swab test by a doctor.
Most often, pimples are accompanied by a single whitehead or blackhead. Whiteheads can appear as a raised bump that can be either red or, when filled with pus, yellow or white (hence the phrase “whitehead”).
In distinction to cold sores, a pimple normally occurs as a single, individual whitehead or blackhead — but in some cases, pimples can also develop in clusters, which can be mistaken for a herpes sore.
The sensation from the sore is very helpful in determining if it's a cold sore or pimple. Cold sores are often associated with a tingling or burning sensation that could develop into a shooting, throbbing, or stinging pain. These sensations may fluctuate as the cold sore develops.
As mentioned, pimples can be painless, but it's possible for them to cause discomfort.
Because sores from a cold sore condition are among several symptoms of herpes, the concurrence of other such symptoms helps narrow down the cold sore vs pimple question. As pimples are almost nothing but a clogged pore, the onset of multiple herpes symptoms combined with a lip sore is one of the clearest indications that it is a cold sore, not a pimple.
Herpes symptoms differ widely between individuals. Besides the sores themselves and the itching or tingling sensations that sometimes accompany them, the following other symptoms are possible:
Note that these symptoms are more likely to occur in genital herpes, not oral herpes — but it is still possible to experience these symptoms from oral herpes.
The most helpful way to correlate other herpes symptoms with a lip sore is the itching or tingling sensation that sometimes accompanies cold sores, as described above. If you felt a tingling, itching, or slightly burning sensation in the same area that the sore later appeared, it would be wise to treat it as a cold sore and take precautions to prevent it from spreading.
If you suspect a sore on or around the lip is a cold sore, it's important to treat it as early as possible to prevent it from spreading. They are highly contagious and can spread both on your own lips and to others.
Consider trying treatments, such as topical creams or patches, that can reduce the duration and frequency of cold sore outbreaks.
Uncertainty over a cold sore vs. a pimple on the lip can be incredibly aggravating, as they appear so similar, especially at first. However, they progress quite differently, and cold sores sometimes occur alongside other symptoms.
With enough knowledge about how cold sores and pimples change over time, you should be able to notice the key differences to know whether you're dealing with a cold sore or pimple.
Cold and canker sores | University Health Service
Herpes or ingrown hair? How to tell the difference | Hims & Hers Health
What are the symptoms of herpes? | Planned Parenthood