Contents
What is pus
Pus is a collection of fluid, white blood cells, microorganisms, and cellular material that indicates the presence of an infected wound or abscess. Pus contains the germs, fluids, and cells the body has shed — basically anything that the body wants to get rid of.
Although pus is normally of a whitish-yellow hue, changes in the color can be observed under certain circumstances. Pus is sometimes green because of the presence of myeloperoxidase, an intensely green antibacterial protein produced by some types of white blood cells. Green, foul-smelling pus is found in certain infections of Pseudomonas aeruginosa. The greenish color is a result of the bacterial pigment pyocyanin that it produces. Amoebic abscesses of the liver produce brownish pus, which is described as looking like “anchovy paste”. Pus from anaerobic infections can more often have a foul odor 1.
In almost all cases when there is a collection of pus in the body (abscess), the clinician will try to create an opening to drain it.
An abscess is a cavity filled with pus (pyoderma or sepsis). An abscess contains white blood cells, dead tissue and bacteria. Abscesses can form on the skin, under the skin, in a tooth, or inside the body. Some people feel sick when they have an abscess. They might get a fever that makes them feel too hot or too cold.
Cutaneous abscesses may occur anywhere on the skin, but are most common under the arms, at the base of the spine (pilonidal disease) or around the genitals (e.g. Bartholin abscess) and anus.
An abscess usually presents as a hot, red, swollen and painful lump. It may lead to fever, swollen lymph nodes, and illness including potentially dangerous septicemia. Non-bacterial abscesses may be cool, skin colored and painless.
If not treated, an abscess eventually bursts and drains thick yellow pus.
Although it may become ‘walled off’ by an inflammatory reaction, an abscess is not surrounded by a true capsule.
If the skin abscess opens on its own and drains, and the infection seems to clear up in a couple of days, your skin should heal on its own. If it doesn’t, it’s time for your mom or dad to call your doctor’s office. If you go to the doctor, he or she will probably prescribe a type of medicine called antibiotics. They help your body kill the germs that are causing the abscess.
Sometimes the doctor will want to drain the abscess to let all the pus and germs out. This will allow the abscess to heal. The doctor might put gauze into the wound to soak up the drainage and help the abscess heal. Gauze is a bit like the white pad on a bandage that rests against a cut or scrape.
Make sure to follow your doctor’s instructions about how to take care of the abscess when you go home. And be sure to tell an adult if you don’t feel better or the abscess gets worse. Ask your parents for your own washcloth and towels so you don’t spread germs to other people.
Is pus bad?
Yes. A collection of pus in your brain may progress to meningitis, cortical venous thrombosis, or brain abscess. Without treatment, coma and death occur rapidly, particularly in subdural empyema.
What causes pus
A painful abscess is usually due to acute bacterial infection. Bacteria penetrate a break in the skin such as a puncture wound, or via a hair follicle. Abscess may also develop around a foreign body, such as a splinter.
The most common causes of infective abscesses are:
- Staphylococcus aureus; the usual cause of boils (furuncles and carbuncles, the most common form of cutaneous abscess), wound infection or infected eczema.
- Methicillin resistant Staphylococcus aureus (MRSA), which may cause recurrent abscesses.
- Streptococcus pyogenes; the usual cause of cellulitis and erysipelas
- Mycobacterium tuberculosis (TB) and atypical mycobacterial infection
- Anaerobes, gram negative organisms, rare bacterial infections and mixed infections
- Fungal infection, eg kerion
- Severe viral infection eg herpes simplex
- Infestations or parasitic infections
In most mucus membranes, anaerobes outnumber aerobic and facultative bacteria in ratios ranging from 10:1 to 10,000:1, with anaerobic gram-negative bacilli microorganisms predominating 2. Species of the Bacteroides fragilis group that colonize the gastrointestinal tract are usually isolated in intra-abdominal and rectal abscesses; pigmented Prevotella, Porphyromonas, and Fusobacterium spp. that colonize the oral cavity are present mainly in oral cavity abscesses, and Prevotella bivia and Prevotella disiens that predominate in the cervical canal are most often recovered in pelvic abscesses. The predominant aerobes and facultative organisms in abdominal and rectal abscesses are Enterobacteriaceae and staphylococci, and Neisseria gonorrhoeae are common in pelvic abscesses (Table 1). Fungi (e.g., Aspergillus) and protozoa (e.g., Toxoplasma gondii, particularly in HIV-infected patients) can also cause abscesses.
Table 1. Predominant bacteria from abscesses
| Abdominal | Urogenital | Head and neck | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Parameter | Abdomen | Retroperitoneal | Diverticulitis | Perirectal | Liver | Spleen | Pancreatic | Subphrenic | Burtholm’s cyst | Prostate | Testicular | Scrotal | Periapical | Cervical lymphadenitis | Parotic | Peritonsillar | Retropharyngeal |
| Reference | 6 | 20 | 19 | 25 | 23 | 23 | 21 | 24 | 6 | 6 | 6 | 6 | 26 | 22 | 28 | 29 | 10 |
| No. of patients | 83 | 161 | 22 | 144 | 48 | 29 | 46 | 52 | 26 | 3 | 6 | 15 | 32 | 40 | 23 | 34 | 14 |
| No. of aerobic bacteria | |||||||||||||||||
| S. pyogenes | 1 | 9 | 3 | 1 | 4 | 1 | 4 | 1 | 10 | 3 | |||||||
| Enterococcus spp. | 19 | 3 | 9 | 8 | 3 | 11 | 9 | 1 | 5 | ||||||||
| S. aureus | 11 | 1 | 34 | 4 | 4 | 6 | 5 | 2 | 1 | 5 | 1 | 8 | 8 | 6 | 5 | ||
| M. catarrhalis | 5 | 2 | |||||||||||||||
| Haemophilus spp. | 1 | 2 | 2 | 7 | 4 | ||||||||||||
| E. coli | 57 | 60 | 15 | 19 | 11 | 5 | 18 | 28 | 6 | 2 | 1 | 1 | |||||
| K. pneumoniae | 8 | 20 | 3 | 3 | 5 | 3 | 12 | 3 | 2 | 1 | |||||||
| P. aeruginosa | 4 | 9 | 1 | 4 | 2 | 1 | 5 | 3 | 2 | 1 | |||||||
| Enterobacter spp. | 1 | 8 | 1 | 4 | 4 | 1 | |||||||||||
| Proteus spp. | 2 | 8 | 1 | 12 | 2 | 3 | 3 | 4 | 3 | 1 | 1 | ||||||
| S. marcescens | 6 | 1 | 3 | 3 | 3 | ||||||||||||
| N. gonorrhoeae | 4 | 2 | 1 | 4 | |||||||||||||
| Other | 20 | 2 | 16 | 1 | 6 | 2 | 3 | 2 | |||||||||
| Enterobacteriaceae | |||||||||||||||||
| Subtotal | 107 | 204 | 35 | 131 | 43 | 23 | 77 | 83 | 24 | 6 | 3 | 15 | 23 | 18 | 16 | 49 | 26 |
| Anaerobic bacteria | |||||||||||||||||
| Peptostreptococcus spp. | 24 | 95 | 6 | 72 | 18 | 11 | 26 | 33 | 12 | 1 | 3 | 7 | 18 | 5 | 5 | 16 | 18 |
| Veillonella spp. | 2 | 10 | 1 | 6 | 3 | 1 | 6 | 6 | 2 | 1 | 2 | 1 | 5 | 3 | |||
| Eubacterium spp. | 2 | 6 | 1 | 11 | 1 | 4 | 1 | 2 | 1 | 1 | 4 | ||||||
| P. acnes | 13 | 2 | 3 | 3 | 4 | 4 | 1 | 4 | 4 | 3 | 1 | ||||||
| C. perfringens | 6 | 10 | 2 | 4 | 5 | 2 | 4 | 6 | 1 | ||||||||
| Clostridium spp. | 13 | 13 | 3 | 11 | 5 | 1 | 3 | 7 | 2 | 2 | |||||||
| Fusobacterium spp. | 4 | 14 | 1 | 21 | 10 | 3 | 5 | 5 | 2 | 9 | 3 | 11 | 14 | ||||
| B. fragilis | 47 | 34 | 14 | 58 | 7 | 2 | 6 | 11 | 3 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | |
| B. fragilis groupa | 11 | 32 | 7 | 27 | 6 | 3 | 11 | 14 | 2 | 1 | 2 | 1 | |||||
| P. melaninogenica | 5 | 5 | 2 | 18 | 1 | 1 | 2 | 2 | 2 | 1 | 2 | 3 | 3 | 1 | 7 | 10 | |
| P. intermedia | 7 | 12 | 2 | 2 | 3 | 3 | 1 | 1 | 2 | 2 | 3 | 3 | 4 | ||||
| P. asaccharolytica | 4 | 3 | 1 | 20 | 3 | 1 | 2 | 1 | 2 | 5 | 4 | ||||||
| P. oralis | 2 | 2 | 1 | 1 | 4 | 1 | 3 | ||||||||||
| P. disiens | 1 | 6 | 1 | 1 | 1 | ||||||||||||
| P. bivia | 2 | 14 | 4 | 3 | |||||||||||||
| Bacteroides spp. | 3 | 12 | 1 | 19 | 4 | 7 | 6 | 1 | 6 | 4 | 2 | 1 | 4 | 11 | |||
| P. gingivalis | 7 | ||||||||||||||||
| Subtotal | 128 | 268 | 37 | 325 | 73 | 33 | 81 | 111 | 43 | 4 | 8 | 28 | 55 | 24 | 20 | 58 | 78 |
| Total | 235 | 472 | 72 | 256 | 116 | 56 | 158 | 194 | 67 | 10 | 11 | 33 | 78 | 42 | 36 | 107 | 104 |
Footnote: a) Other than B. fragilis.
[Source 2 ]Infective abscesses may affect healthy people, but they are more common in the following circumstances.
- Metabolic syndrome and obesity
- Smoking
- Diabetes
- Immune compromise
- IV drug users
A sterile abscess may persist after infection has been cleared, as it contains dead or necrotic tissue and inflammatory cells.
Sterile abscess may occur after corticosteroid injection. This is more likely when the medication has spilled into subcutaneous fat. A foreign-body or other hypersensitivity reaction to injected material such as bovine collagen may also result in abscess formation.
Certain inflammatory skin diseases may cause tissue destruction and abscess formation, in the absence of pathogens (infectious microbes). These include:
- Hidradenitis suppurativa
- Acne conglobata and acne fulminans
- Crohn skin disease
- Panniculitis (inflamed subcutaneous fat)
How to get rid of pus
An abscess should be explored to remove foreign bodies, and its contents should be removed. This requires making a surgical incision and draining the pus. The cavity is then thoroughly washed out with saline. It should be left open to allow further pus to drain away. Wicks are sometimes inserted if the abscess is deep, to help it drain.
Antibiotics are often prescribed, chosen according to the organism causing the abscess and its sensitivities.
Prevention of further abscess formation
If abscesses are due to staphylococcal infection, the risk of recurrence can be minimized by:
- Hygiene: wash hands frequently (or use hand rubs) and do not share towels, clothing, razors and tooth brushes.
- Reduce transmission to others: while infected, do not share equipment at a community gym or attend sauna or swimming pool.
- Dispose of tissues and dressings in sealed bag or burn them.
- Take care not to nick skin while shaving
- Eat plenty of fresh fruit and vegetables
- Aim for normal weight and do not smoke.
- Topazian RG, Goldberg MH, Hupp JR (2002). Oral and maxillofacial infections (4 ed.). Philadelphia: W.B. Saunders. ISBN 978-0721692715.[↩]
- Brook I. Abscesses. In: Brogden KA, Guthmiller JM, editors. Polymicrobial Diseases. Washington (DC): ASM Press; 2002. Chapter 9. Available from: https://www.ncbi.nlm.nih.gov/books/NBK2497[↩][↩]
