Embarrassing Illnesses

There are several different causes of otitis externa and a number of factors that may provoke the condition, making it more likely to occur. However, in many cases of the condition, particularly of chronic otitis externa, the cause remains unknown.

The causes of the three different types of otitis externa, plus the provoking factors of the condition, are detailed below.

Causes of localised otitis externa

Localised otitis externa is caused by an infection of a hair root (follicle) in your ear canal. The infection is usually the result of bacteria called Staphylococcus aureus.

Causes of acute diffuse otitis externa and chronic otitis externa

The causes of both acute diffuse otitis externa and chronic otitis externa are essentially the same, although in many cases of chronic otitis externa, the cause is unknown. Causes may include:

• Bacterial infection - this is a common cause of acute otitis externa. The bacteria that cause the infection are usually Pseudomonas aeruginosa, or Staphylococcus aureus. In chronic otitis externa, there may be a chronic low-grade infection, which is difficult to diagnose.
• Seborrhoeic dermatitis - this is a common skin condition in which the areas of your skin that are naturally greasy (sebaceous), such as the side of your nose, your forehead and your scalp, become irritated and inflamed (swollen). This may be a contributory factor in the development of otitis externa.
• Middle ear infection - if you have had a middle ear infection, such as otitis media, your ear may have been producing discharge over a prolonged period of time. In some cases, the discharge may cause otitis externa.
• Fungal infection - the species of fungus that can cause otitis externa include the Aspergillus variety, and the Candida albicans variety which also causes thrush. If you have been using antibacterial ear drops, or aural corticosteroids (ear medication that relieves swelling), over a long period of time to treat another infection, you may develop a secondary fungal infection that can cause otitis externa.
• Allergic and irritant reactions - otitis externa can be caused by an allergic or irritant reaction to something that comes into contact with your ears, such as ear medication, ear plugs, or shampoo. If you wear a hearing aid, you may find that it makes the inside of your ear sweaty and, in some cases, this can cause otitis externa.

Factors that can provoke otitis externa

These factors are not direct causes of otitis externa, but they may make getting the condition more likely.

• Ear damage - your ear canal is very sensitive and may easily suffer damage through scratching, excessive cleaning, ear syringing and the insertion of cotton buds. You may also damage your ear canal by incorrectly, or excessively, wearing hearing aids, ear plugs or ear phones.
• Excessive moisture - you are more likely to get otitis externa if liquid gets into your ear canal. Therefore, swimming (particularly in dirty, or polluted water), sweating and humid environments may increase your risk of getting the condition.
• Chemicals - if you use products in or near your ears that contain chemicals such as hair sprays, hair dyes and earwax softeners, your chances of getting otitis externa are increased.
• Underlying skin conditions - as well as seborrhoeic dermatitis being a background factor in some cases of otitis externa, you may be more at risk of getting the condition if you have an underlying skin condition such as psoriasis, eczema or acne.