Condition category
Signs and Symptoms
Date applied
Date assigned
Last edited
Retrospectively registered
Overall trial status
Recruitment status
No longer recruiting

Plain English Summary

Background and study aims
Upper respiratory tract illness (URTI) is the most common respiratory illness experienced by the general population and sore throat is the most common URTI managed in the NHS, costing the NHS an estimated £25 million in consultations alone. Antibiotic use for respiratory tract illnesses has decreased since 1997 but is still double the rate of other Northern European countries, and costs the NHS an additional £6-12 million in prescribing costs per annum. Xylitol (used in some sugar-free gum) is a birch sugar, and causes local 'bacterial interference' by inhibiting the growth and adherence of bacteria to the throat. Sorbitol has no such effect and will be used as a 'placebo' (dummy) gum. Probiotics, which are also available commercially, are benign non-pathogenic bacteria and may also act through local 'bacterial interference' by a different mechanism and may also have an effect on non-specific general activation of the immune system. Although there are studies that support the use of both xylitol and probiotics in the management of recurrent infections, this evidence needs confirming, and we particularly need evidence about their effectiveness for either symptoms or recurrence of sore throat. In addition there is no clear evidence concerning the effect of chewing any kind of gum on the symptoms of sore throat. The effectiveness of chewing xylitol and probiotics in URTIs requires urgent clarification both for the general public and for the health service. Since probiotics and xylitol act via different mechanisms, a study is needed to assess the possible interaction of both interventions together. This study aims to investigate the effect of xylitol and probiotics on symptoms and recurrence of sore throat.

Who can participate?
Patients over the age of 16, presenting with acute sore throat

What does the study involve?
Participants are provided with instructions and randomly allocated to receive a treatment pack containing 3 months' supply of either just probiotic capsules (to take one capsule daily) or probiotic capsules and chewing gum (to chew five pieces a day). As some people get better just because they are taking something they believe to be helpful (a placebo), some of the packs have pretend treatments in them - they look and taste the same as the real thing and participants won't know which one they've got until the end of the study.

What are the possible benefits and risks of participating?
Not provided at time of registration

Where is the study run from?
The study was lead and run by the trial management team in Southampton, and participants were recruited from 83 practices from Land's End to Ipswich (UK)

When is the study starting and how long is it expected to run for?
November 2008 to January 2015

Who is funding the study?
National Institute for Health Research (NIHR) (UK)

Who is the main contact?
Ms Tammy Thomas

Trial website

Contact information



Primary contact

Ms Tammy Thomas


Contact details

Aldermoor Health Centre
Aldermoor Close
SO16 5ST
United Kingdom

Additional identifiers

EudraCT number number

Protocol/serial number


Study information

Scientific title

A primary care randomised controlled trial of probiotics, xylitol and sorbitol for acute sore throat



Study hypothesis

This study aims to investigate the effect of xylitol and probiotics on symptoms and recurrence of sore throat.

Ethics approval

Southampton and South West Hampshire REC, 28/02/2005, ref: 05/Q1702/11

Study design

Randomised interventional treatment trial

Primary study design


Secondary study design

Randomised controlled trial

Trial setting

GP practices

Trial type


Patient information sheet

Not available in web format, please use the contact details to request a patient information sheet


Topic: Primary Care Research Network for England; Subtopic: Not Assigned; Disease: All Diseases


Patients will be approached by either advertising in the practice, when seeing their doctor/nurse (who will provide information to the patient with the consent form) or by writing to patients with known recurrent sore throat identified from a database search. Patients who agree to take part will be allocated treatment packs in numerical order provided by the investigators with the surgery recording ID numbers.

Probiotics, sorbitol and xylitol for acute sore throat. Patients randomised to probiotics/placebo will be required to take one capsule per day for 3 months. Patients randomised to chew active/placebo gum will be asked to chew five pieces per day (for 5 minutes) for 3 months. All treatment groups will be followed up for a further 3 months.

Follow-up length: 6 months
Study entry: single randomisation only

Intervention type



Not Applicable

Drug names

Primary outcome measure

The mean score for sore throat and difficulty swallowing during 2 - 5 days after presentation

Secondary outcome measures

1. Time to resolution of sore throat
2. Time taken off work or unable to do normal activities
3. Satisfaction with treatment

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

1. Presenting with acute sore throat
2. Over the age of 16 years, either sex

Participant type


Age group




Target number of participants

Planned Sample Size: 401; UK Sample Size: 401

Participant exclusion criteria

1. History suggestive of quinsy
2. Previous rheumatic fever, glomerulonephritis
3. Phenylketonuria
4. Allergy to xylitol, sorbitol or probiotics
5. Patients unwilling or unable to self medicate with gum or probiotics for the duration of the study or complete outcome measures
6. Subjects with serious chronic disorders where antibiotics are automatically needed (e.g. cystic fibrosis)
7. Suspected pregnancy
8. Immune deficiency

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

Aldermoor Health Centre
SO16 5ST
United Kingdom

Sponsor information


University of Southampton (UK)

Sponsor details

University Road
SO17 1BJ
United Kingdom

Sponsor type




Funder type


Funder name

Programme Grants for Applied Research (ref: RP-PG-0407-10098)

Alternative name(s)

NIHR Programme Grants for Applied Research, PGfAR

Funding Body Type

government organisation

Funding Body Subtype

Federal/National Government


United Kingdom

Results and Publications

Publication and dissemination plan

Not provided at time of registration

Intention to publish date

Participant level data

Not provided at time of registration

Basic results (scientific)

Publication list

2017 results in:

Publication citations

Additional files

Editorial Notes

15/02/2018: Publication reference added. 21/08/2014: The overall trial end date was changed from 01/07/2011 to 01/01/2015.