An investigation was launched after a member of staff at McDonalds in Commercial Road, Portsmouth was sprayed in the face with a substance at around 6.45pm on Sunday 9 September.
Initially it was not known what it was and therefore fire, ambulance and police were all called to the scene.
However, it is now believed the substance was perfume.
The victim, a 22-year old man, was taken to the Queen Alexandra Hospital for treatment and was later discharged with no lasting injuries.
A 13-year-old girl from Fratton was arrested on suspicion of administer poison / noxious thing with intent to injure / aggrieve / annoy. She was de-arrested when she arrived in custody and will attend a voluntary interview later today.