Cold sore vs spot on the lip: how to tell them apart

A bump on or beside the lip is one of the most common things people look at in the mirror and worry about. A cold sore and a spot can both appear on the lip border, both can be red, sore and swollen, and in the early hours neither may have a clear identity. The question is practical rather than academic, because a cold sore is infectious and a spot is not, and the treatments differ.

The NHS cold sores page deals with this directly with a short "when it's not a cold sore" list: a painful red spot on the face filled with pus is a spot or boil, a blister on the inside of the lip or mouth is a mouth ulcer, and red sores or blisters on the face that become crusty, golden-brown patches suggest impetigo.

The table combines the NHS descriptions of cold sores and acne spots. It is a guide, not a diagnostic tool.

The NHS describes a typical cold sore as starting with tingling, itching or burning, followed within about 48 hours by one or more painful blisters on the face. The blisters are usually small and filled with fluid. They then burst and crust over into a scab. The process should start to heal within 10 days, though the area may be irritating or painful in the meantime.

Triggers named by the NHS include illness, sunshine and being on your period. It also lists sunbeds and strong sun on the lips as things to avoid, and recommends sunblock lip balm (SPF 15 or above) outdoors.

The cause is the herpes simplex virus. The NHS says most people are exposed to it as children through close skin-to-skin contact such as kissing someone who has a cold sore. Once you have the virus it stays in your skin for the rest of your life and sometimes causes a cold sore, which explains why they return in the same spot.

The NHS acne page describes the range of acne spots: whiteheads are small skin-coloured bumps, blackheads are flat or slightly raised black or brown spots, papules are raised bumps that look pink or red on white skin and brown or purple on brown and black skin, pustules are raised bumps filled with pus, and nodules and cysts are larger, painful lumps under the skin. Acne usually affects the face, chest and back.

A boil, listed by the NHS cold sore page as a possible alternative, is a painful red spot filled with pus. Because neither a plain acne spot nor a boil begins with blisters that burst and crust, the sequence, tingling first and then fluid-filled blisters, is the main clue pointing to a cold sore.

The NHS advises not picking or squeezing spots because this can cause scars. The NHS also says not to touch a cold sore, apart from applying cream, because cold sores can easily spread to other people and other parts of your body.

For a cold sore the NHS says a pharmacist can recommend creams to ease pain and irritation, antiviral creams to speed up healing and cold sore patches to protect the skin. If you regularly get cold sores, antiviral creams should be used as soon as you recognise the early tingling, because they do not always work once blisters appear. Paracetamol or ibuprofen can ease pain and swelling, and you should drink plenty of fluids. Do not give aspirin to children under 16. The NHS says not to touch the cold sore apart from applying cream, to dab cream on rather than rub it in, and to wash your hands before and after.

Because cold sores are contagious, the NHS advises washing hands with soap and water after touching the area, not kissing anyone while you have a cold sore, and avoiding oral sex until it has healed, as you could give your partner genital herpes. It specifically warns that kissing a baby with a cold sore can lead to neonatal herpes, which is very dangerous to newborn babies.

For acne spots the NHS suggests washing the skin twice a day with a gentle cleanser, using non-comedogenic products, and trying treatments such as salicylic acid or benzoyl peroxide, with a pharmacist able to advise.

The NHS says to see a GP about a cold sore if it has not started to heal within 10 days, you are worried about it or think it is something else, it is very large or painful, you or your child also have swollen, painful gums and sores in the mouth (gingivostomatitis), or you have a weakened immune system, for example because of chemotherapy or diabetes. A GP may prescribe antiviral tablets if cold sores are very large, painful or keep coming back. Newborn babies, pregnant women and people with a weakened immune system may be referred to hospital.

For acne, the NHS suggests seeing a GP if you have tried treating it yourself and it is not getting better, if you have lots of spots or they are deep, painful or causing scars. The NHS also says to see a GP if you are worried about a cold sore or think it is something else.