Home > ORAL HEALTH > Dental Problems > Recurrent Aphthous Stomatitis (RAS)

Recurrent Aphthous Stomatitis (RAS)

What are recurrent aphthous stomatitis ?

Recurrent aphthous stomatitis (RAS) or recurrent aphthous ulcers (RAU) is a clinical condition whereby there are recurrent episodes of one or more painful, rounded or ovoid ulcers with an area of redness surrounding it. The ulcer base is usually yellow or gray in colour. The size of the ulcers is variable ranging from a few millimetres to larger than one centimetre in diameter. RAS is thought to be a common condition of the mouth affecting up to 20% of the population. RAS is usually classified into one of three clinical types:

  • Minor
  • Major
  • Herpetiform

This classification is usually based on the appearance, number, size, location and duration of the ulcers.

Minor RAS

The most common type affecting the majority of people with RAS.  They are usually smaller than 5mm in diameter and occur in crops of 1 to 5 ulcers at a time. They usually heal by 14 days and without any scarring. The most common sites for this type are the inner surfaces of the cheeks and lips as well as the floor of mouth.

Figure 1.Minor RAS

Major RAS

The second most common type. The ulcers are usually larger, more than 10mm in diameter. They can occur on any surface in the mouth. They take a much longer time to heal, at times they can last for up to 2 months and large ulcers can heal with scarring.

Figure 2: Major RAS

Herpetiform RAS

The least common type. The ulcers can occur in clusters of more than 15 at a time and each ulcer is around 1 – 3 mm in diameter. At times, several smaller ulcers can merge to give rise to larger ulcers. They tend to heal within 2 weeks without scarring. This type is NOT caused by herpes viruses although the name may be suggestive of it.

What is the cause of RAS ?

The precise cause for RAS is not completely understood but there is an immunological factor involved. However, it is known that a number of underlying or precipitating factors can cause or worsen RAS such as:

  • anaemia,
  • vitamin deficiencies,
  • some medications,
  • stress and
  • mechanical trauma from sharp teeth/fillings, dental braces or a tooth brush

At times, RAS can be a component of a more widespread disease affecting other parts of the body such as:

  • Behcet’s disease
  • MAGIC (mouth and genital ulcers with inflamed cartilage) syndrome
  • PFAPA (periodic fever, apthous ulcers, pharyngitis and adenitis)
  • Cyclic neutropenia
  • HIV infection etc

RAS is not infectious. A genetic component is present whereby many people with RAS have a close relative with the same condition.

How is RAS diagnosed?

Diagnosis is largely dependent on the history provided by the patient and clinical findings. RAS is characterized by recurrent episodes of one or more rounded, shallow, painful ulcers at intervals of a few days to a few months. Some patients report of symptoms such as tingling or burning about 2 to 48 hours before the appearance of the ulcers. A comprehensive medical history is necessary and usually blood tests will be arranged to check for any possible underlying / predisposing causes for RAS (as mentioned above). For longstanding ulcers, a biopsy may be performed to rule out other causes of mouth ulceration.

How is RAS treated?

At this point in time, there is no absolute cure for RAS unless it involves an underlying cause which if found and corrected can lead to resolution of RAS. Treatment is usually targeted at reducing / relieving the symptoms associated with RAS and to prevent / reduce secondary infection as well as to promote healing. Choice of treatment is dependent on the severity of the condition and the presence of any underlying medical conditions. The following are some of the medications used to treat RAS:

  • Topical corticosteroids: Commonly used agent as it is usually effective for most patients. Available as pastes, ointments, creams, mouthwashes and sprays.
  • Anaesthetic / Anti-inflammatory mouthwashes or sprays: Usually prescribed if ulcers are numerous and also very helpful before meals.
  • Use of an antiseptic alcohol-free mouthwash: Usually recommended to reduce secondary infection and improve plaque control especially when toothbrushing becomes difficult.
  • Covering agents: Form a mechanical barrier against irritation and secondary infection. Some also promote healing. Usually are in the form of pastes and gels.
  • Systemic corticosteroids: Short-term treatment may be used if the signs and symptoms are severe.

Other types of medication / therapy are reserved for more severe cases of RAS. And these may be associated with a number of side effects which will be explained to you by your attending specialist. Your specialist may recommend changing your toothpaste as some toothpastes contain ingredients that may worsen your symptoms. Any ulcer that show no signs of improvement and persists for more than 2 weeks even after treatment has been initiated should be examined by your dentist who may refer you to a specialist for his/her opinion and possible biopsy.

Fortunately, in most cases, the severity as well as frequency of RAS tend to decrease with age.

Self-care measures

  • Avoid hot, spicy, acidic, salty or hard foods (such as biscuits and toast) when you have ulcers.
  • Have a balanced diet to avoid nutritional deficiencies
  • Have good oral hygiene to prevent secondary infection of ulcers
  • Have routine dental appointments to sort out any sharp teeth or broken fillings that trigger / worsen your ulcers.


The outcome and complications are usually dependent on the severity of the condition as well as the presence of any associated / underlying systemic conditions. RAS by themselves can cause significant discomfort causing decrease in nutritional intake which may in turn worsen the RAS and also cause significant weight loss. Major RAS may mimic infection or cancer and at times a biopsy may be needed to rule these out.


  1. Scully, C. (2008). Oral and maxillofacial medicine- The basis of diagnosis and treatment. (2nd ed.) Elsevier.
  2. S.R. Porter, C. Scully and A. Pedersen; Recurrent Aphthous Stomatitis. Crit Rev Oral Biology & Medicine 1998 9(3): 306 – 321
  3. Scully C, Gorsky M, Lozada-Nur F (2003). The diagnosis and management of recurrent aphthous stomatitis: a consensus approach. J Am Dent Assoc 134: 200–207.
  4. Porter SR, Scully C (2005). Aphthous ulcers: (recurrent) Clin Evid 13: 380–381.
  5. Jurge, S., Kuffer, R., Scully, C. and Porter, S. (2006), Number VI  Recurrent aphthous stomatitis. Oral Diseases, 12: 1–21.
Last Reviewed : 3 June 2014
Writer : Dr. Hans Prakash a/l Sathasivam
Accreditor : Dr. Lau Shin Hin