A pimple is a small pustule or papule. Pimples are small skin lesions or inflammations of the skin - they develop when sebaceous glands (oil glands) become clogged and infected, leading to swollen, red lesions filled with pus.
Pimples are also known as spots or zits
The development of pimples is primarily connected to oil production, dead skin cells, clogged pores and bacteria (although yeast infection can also cause pimples to develop).1,3
Sebaceous glands, which are located at the base of hair follicles, can become overactive due to hormone dysregulation, which is why acne is most commonly associated with puberty, and why breakouts occur around the time of menses.5
The most likely parts of the body to be affected by pimples are the face, back, chest and shoulders due to the proliferation of sebaceous glands in these areas of skin. Pimples are a sign of acne, especially when a breakout occurs.
Dermatologists and other experts are increasingly concerned about the long-term use of antibiotics for acne treatment, and its contribution to bacterial resistance. Experts from the Centre of Evidence-Based Dermatology at the University of Nottingham, England, wrote in The Lancet that although pharmacies are well stocked with a wide range of acne medications, few studies have been carried out regarding their efficacy.
A diagram of the sebaceous glands (image by OpenStax College)
The sebaceous glands are tiny skin glands which secrete sebum - a waxy/oily substance - to lubricate the skin and hair of mammals, including humans.
Sebaceous glands are found all over human skin with the exceptions of the palms and soles. There is a greater concentration of sebaceous glands on the face and scalp. At the rim of the eyelids, Meibomian or tarsal glands are a special kind of sebaceous gland that secrete meibum, a special type of sebum that helps maintain the eye's tear-film by preventing evaporation.
Several medical conditions are linked to an abnormality in sebaceous gland function, including:
- Acne (pimples).
- Sebaceous cysts - closed sacs or cysts below the surface of the skin.
- Hyperplasia - the sebaceous glands become enlarged, producing yellow, shiny bumps on the face.
- Sebaceous adenoma - a slow-growing tumor (benign, non-cancerous) usually presenting as a pink, flesh-colored, or yellow papule or nodule.
- Sebaceous gland carcinoma - an aggressive (cancerous) and uncommon skin tumor.
If a breakout occurs, doctors recommend that pimples be treated promptly to prevent the risk developing severe acne. There is also the danger that untreated severe acne may result in visible scars on the skin.
Causes of pimples / zits
The sebaceous glands, which produce sebum, exist inside the pores of our skin. The outer layers of our skin are being shed continuously.
Sometimes, dead skin cells are left behind and get stuck together by the sticky sebum, causing a blockage in the pore.
Pore blockage is more likely to occur during puberty (the process of physical changes by which a child becomes an adult capable of reproduction) as the sebaceous glands produce more sebum at this time.
Where sebum and dead skin cells accumulate and block a pore, this encourages the growth of undesirable bacteria, including Propionibacterium acnes - the slow-growing bacterium linked to acne.
Propionibacterium acnes generally exists harmlessly on our skin; however, when the conditions are right, it can reproduce more rapidly and become a problem. The bacterium feeds off the sebum and produces a substance that causes an immune response, leading to skin inflammation and spots.
Researchers at the Washington University School of Medicine identified two unique strains of P. acnes in the skin of 20% of people with pimples, while those with healthy skin tended not to harbor these strains. The situation was reversed for another strain of P. acnes: those with pimples tended not to harbor this strain, but it was present in healthy skin. As such, it seems that particular types of bacteria determine the severity and frequency of pimples.
Pimples and acne have also been linked to yeast infections, with a group of yeasts called Malassezia thought to be the key culprit. These yeasts grow on the skin of the forehead and chest, but rarely on the sides of the face, and do not inhabit the same pores as P. acnes. As such, treatments that seek to eradicate these yeasts or P. acnes can unwittingly create ideal conditions for the other.3
People prone to acne have been found to have skin that is especially sensitive to normal blood levels of testosterone - a natural hormone found in both males and females. In such people, testosterone can trigger the sebaceous glands to produce excess sebum, increasing the likelihood of clogged pores.
Despite being related to bacterial infection, pimples are not contagious. You cannot catch pimples from another person.
Researchers from New York University reported in the Journal of the Academy of Nutrition and Dietetics that dairy products and high glycemic index foods are linked to pimples. The researchers found that people who eat a lot of high glycemic index foods and dairy products are more likely to have acne. They also suggested that using medical nutrition therapy may help in the treatment of acne.
In addition to following a low-Glycemic Index, dairy-free diet, it is also helpful to ensure a good intake of healthy polyunsaturated and monounsaturated fats. Despite pimples being caused by blocked pores due to excess sebum production, fat-free or very low-fat diets are not recommended for acne as too little fat in the diet can actually dry out the skin and prompt the body to ramp up sebum production.
A good intake of fats from nuts, seeds, and olive oil appears to help by keeping inflammation in check; supporting the body in maintaining healthy blood sugar levels; and maintaining good skin moisture levels so as to provide an effective barrier and immune response to prevent bacterial infection.2
Having pimples or acne can be hereditary.
Symptoms of pimples
There are several different types of pimples and they have different signs and symptoms:
- Whiteheads - also known as a closed comedo. These are very small and remain under the skin, appearing as a small, flesh-colored papules.
- Blackheads - also known as an open comedo. These are clearly visible on the surface of the skin and are black or dark brown due to the oxidation of melanin, the skin's pigment. Some people mistakenly believe they are caused by dirt, because of their color, and scrub their faces vigorously - this does not help and may irritate the skin and cause other problems.
- Papules - these are small, solid, rounded bumps that rise from the skin. The bumps are often pink.
- Pustules - these are pimples full of pus. They are clearly visible on the surface of the skin. The base is red and the pus is on the top.
- Nodules - these are morphologically similar (similar structure) to papules, but larger. They can be painful and are embedded deep in the skin.
- Cysts - these are clearly visible on the surface of the skin. They are filled with pus and are usually painful. Cysts commonly cause scars.
Image © Designua | Dreamstime.com
How common are pimples (acne)?
Acne is the most common skin condition in adolescents. According to a review in the British Medical Journal:4
- More than 80% of teenagers get acne at some point.
- A community sample of 14 to 16 year-olds in the United Kingdom revealed that acne affected 50% of them.
- A sample study of adolescents in New Zealand found acne was present in 91% of boys and 79% of girls.
- A sample study of adolescents in Portugal found that the average prevalence of acne (in both sexes) was 82%.
- 30% of teenagers with acne required medical treatment because of its severity.
- General practitioners (GPs, primary care physicians) in the UK reported that 3.1% of 13 to 25 year-old patients visited them complaining of acne.
- The incidence of acne is similar in both adult males and females.
- Doctors report that acne appears to peak at 17 years of age.
- Acne incidence (presence, occurrence) in adults is increasing, doctors report. We do not know why.
In our next article, we look at over-the-counter treatments and prescription treatments for pimples, zits and acne. You can read it here.