Systematic desensitisation looks to reduce phobic anxiety via the gradual exposure to the phobic stimulus.
how
Firstly, an anxiety hierarchy is created where situations involving presence of phobic stimulus are ranked from least to most scary e.g., 0=seeing picture of a spider, 10=holding a spider in your hand. Next the therapist teaches the patient relaxation techniques e.g., deep breathing or meditation. Finally, the patient is gradually exposed to anxiety hierarchy, move up the hierarchy when relaxed at that stage.