Grass pollen extracts

How it works

Repeated controlled exposure to the allergen induces immune tolerance, shifting the response away from allergen-specific IgE and promoting regulatory T-cell activity and blocking IgG antibodies.

Prescribing in practice

• Carries a risk of systemic allergic reactions including anaphylaxis, so initiation (particularly subcutaneous products) must occur where resuscitation facilities and trained staff are immediately available, with a period of observation after dosing.
• Should be initiated and supervised by clinicians experienced in allergen immunotherapy, with treatment typically started before the pollen season and continued for a prolonged course.
• Caution or avoidance in poorly controlled or severe asthma, which increases the risk of serious systemic reactions; refer to the SPC for the specific product.

Monitoring

Monitor for local and systemic allergic reactions during and after administration, with closer observation at initiation and after dose escalation.

Counselling the patient

• You may notice itching or swelling in the mouth or at the injection site, which usually settles as treatment continues.
• Seek urgent help if you develop widespread rash, breathlessness, wheeze, or facial swelling.
• Benefit builds gradually and the full course must be completed for lasting effect.

Evidence & guidelines

Allergen immunotherapy for allergic rhinitis is supported by international allergy guidelines and is recognised by NICE as a treatment option for selected patients with severe, persistent symptoms uncontrolled by standard therapy.