Allergic Rhinitis and Orthodontic Treatment

How allergic rhinitis causes mouth breathing

Allergic rhinitis causes inflammation and oedema of the nasal mucosa, leading to varying degrees of nasal obstruction. When nasal breathing is obstructed, whether continuously or during sleep and exercise, the body switches to mouth breathing as an alternative airway. While occasional mouth breathing during an acute allergic episode is harmless, habitual mouth breathing — particularly during the years of active jaw and facial development in childhood — alters the pattern of muscular forces acting on the developing jaws and teeth. The tongue, which normally rests against the palate during nasal breathing and acts as an internal scaffolding for palatal width, drops to a lower resting position during mouth breathing, reducing its stimulatory effect on palatal development.

Effects on jaw and facial development: the adenoid face pattern

Chronic mouth breathing during childhood and adolescence is associated with a recognised pattern of dentofacial changes often described as the adenoid face or long face syndrome. Characteristic features include a high, narrow palate (high arched palate), increased anterior face height (long lower third of the face), anterior open bite (front teeth not meeting), retrognathia (recessed lower jaw), and an increased overjet. The upper dental arch becomes narrow and crowded. These changes occur because nasal breathing, with the lips sealed and the tongue resting on the palate, provides an internal widening force on the developing maxilla; without it, the palate develops more narrowly. Mouth breathing also alters the position and function of the circumoral muscles, affecting the labial pressure on upper incisors.

Palate expansion and nasal airflow

Rapid palatal expansion (RPE) or slow palatal expansion using a palatal expander appliance widens the maxillary arch by opening the midpalatal suture. Because the nasal floor forms the roof of the mouth, maxillary expansion simultaneously widens the nasal floor and increases nasal cross-sectional area. Studies using acoustic rhinometry and peak nasal inspiratory flow have shown objectively measurable improvements in nasal airway volume following palatal expansion in children. For patients with allergic rhinitis and a high narrow palate, palatal expansion can therefore address both the dental problem — narrow arch, crowding, crossbite — and contribute to improved nasal breathing. This makes early palatal expansion, before the midpalatal suture fuses in mid to late adolescence, a particularly valuable intervention in children with allergic rhinitis.

The orthodontic-ENT referral pathway for children

Children with suspected mouth breathing, adenoid face features, or habitual open mouth posture should ideally be assessed by both an orthodontist and an ear, nose, and throat (ENT) surgeon. ENT assessment can identify enlarged adenoids or tonsils contributing to nasal obstruction, as well as intrinsic nasal problems such as septal deviation or turbinate hypertrophy. Adenotonsillectomy — surgical removal of enlarged adenoids and tonsils — can significantly improve nasal airway patency and, when performed before extensive facial growth changes have occurred, may reduce the severity of resulting orthodontic problems. The orthodontist and ENT surgeon should communicate about timing: orthodontic expansion is more effective when the nasal airway obstruction has been addressed simultaneously or beforehand. NHS referral to ENT via the GP is the standard pathway; orthodontic referral is available under NHS for eligible children.

Antihistamines and steroid nasal sprays: oral health effects

Antihistamines — both first-generation (e.g. chlorphenamine) and second-generation (e.g. cetirizine, loratadine) — reduce allergic symptoms but have significant xerostomic (dry mouth) effects, particularly first-generation antihistamines due to their anticholinergic activity. Dry mouth reduces the protective, buffering, and antimicrobial benefits of saliva, increasing the risk of dental caries, erosion, and gingival problems — all of which are heightened around orthodontic appliances. Intranasal corticosteroid sprays (e.g. fluticasone, mometasone) are the most effective treatment for perennial allergic rhinitis and have minimal systemic absorption; their direct effect on oral tissues is negligible. However, patients using steroid sprays should be instructed in correct technique to avoid spraying directly onto oral tissues. Saline nasal irrigation can be a useful adjunct that does not cause dry mouth.

Managing allergic rhinitis during orthodontic treatment

Before commencing orthodontic treatment, patients with allergic rhinitis should optimise their nasal symptom control. Second-generation antihistamines are preferred over first-generation to minimise dry mouth. Regular intranasal steroid spray use throughout the allergy season or year-round for perennial rhinitis reduces mucosal swelling and nasal obstruction. Staying hydrated and using sugar-free chewing gum to stimulate saliva flow can partially counteract antihistamine-induced dry mouth. Orthodontic appointments during high pollen periods may need to be timed sensitively; some patients find their nasal congestion makes lying back in the dental chair uncomfortable during periods of peak symptoms. Informing the orthodontic team of the diagnosis allows adjustments to appointment management.

Useful related pages

This guide is for general information only. It is not a diagnosis, treatment plan, or substitute for advice from a registered dentist or orthodontist.