The 22-year-old man has been taken to Queen Alexandra Hospital for treatment.
A spokesman for Hampshire Constabulary said: '˜An investigation has been launched after a member of staff at McDonalds in Commercial Road, Portsmouth was sprayed in the face with a chemical substance at around 6.45pm today, Sunday, September 9. '˜It is thought the substance is a CS spray or similar. However initially it was not known what it was and fire, ambulance and police were all called to the scene. '˜We're appealing for any witnesses or anyone with information about the incident to contact us on 101.'
ICYMI:Â British sailors arrested on HMS Queen Elizabeth's first trip overseas toÂ America At this stage no one has been arrested in connection with the incident.Â