Behaviourists argue that all behaviours are learnt therefore one way in which they treat phobias is by systematic desensitisation. This is where phobic anxiety is gradually reduced through counterconditioning. Patients are taught relaxation methods as it is not possible to be relaxed and afraid at the same time. As well as this an anxiety hierarchy is created and patients are gradually exposed to their phobic stimulus whilst in a relaxed state.
Furthermore, another way in which behaviourists treat phobias is flooding. This is when patients are immediately exposed to their phobic stimulus. Patients aren't allowed to avoid the stimulus therefore quickly realise that it is not harmful. This is called extinction as the learned response is extinguished when the conditioned stimulus is encountered without the unconditioned response.