1. to make abnormally or excessively sensitive to a stimulus, allergen, or substance
Usage: British spelling; American equivalent is 'hypersensitize'; commonly used in medical and immunological contexts
2. to cause someone to become overly reactive or defensive about a particular issue or topic
Usage: informal usage

Examples

• Repeated exposure to the allergen can hypersensitise the immune system.
• The medication may hypersensitise patients to sunlight.
• Constant criticism can hypersensitise a child to negative feedback.
• The treatment aims to hypersensitise cancer cells to radiation therapy.
• Don't hypersensitise the issue by bringing it up repeatedly.
• Certain chemicals can hypersensitise the skin to irritants.