This is an alternative approach and might not be for everyone - but could be worth considering....
This book puts forward the theory that the body is over reacting to a whole host of stressors and it is the pollens (or whatever ..) that tips the body over the edge so if you remove many of the controllable factors that are adding stress to the body, your body might be able to cope with the pollens.
This approach, along with homeopathy, which in part involved creating a remedy from the pollens and chemicals that DS was reacting to, has worked for my son. Food is a big factor (sugar, dairy, tomatoes, beef, gluten - he can tolerate them, but if he reduces these, he is less likely to have other symptoms), he sleeps on a wool mattress, foam is not good for him, nor are many of the perfumed chemicals in so many things, we have no carpets. Every time he displaying hay fever symptoms, we have been able to track down another thing that he is being exposed to, when removed, his hay fever symptoms diminish. We often say - he is sneezing - that must be X. (currently it is hair products!).
It has been quite a journey to identify all of the things that put my son's immune system under pressure, but he is a robust 15 year old now. When he first started showing hay fever symptoms, he was wheezing a lot, and reacting badly to Ventolin so we had to find a way to help him be less reliant on Ventolin.
He also takes high doses of vitamin c and magnesium, when he had symptoms, as this improves his histamine response and reduces inflammation.
My husband used to suffer really badly from hay fever - he takes some homeopathic remedies if needed - maybe for a week or so, every two to three years. Before, he was on antihistamines for months at a time.
The book, despite the title, will not eliminate allergies in 7 days - but it will give you things to think about and ways to support the entire body, which might result in a significant reduction in symptoms.
https://www.amazon.co.uk/7-Day-Allergy-Makeover-Eliminate-Allergies/dp/0399166246/ref=sr_1_1?crid=3F1HAAHCURGEH&dib=eyJ2IjoiMSJ9.qkRR-hQXWBrq6444ujeVNA.V9rgnHRGl2vvbOX5lL75wmXHWlQENoHCWuSiThPVUI8&dib_tag=se&keywords=the+7+day+allergy+makeover&qid=1741105171&sprefix=the+7+day+allergy+makeover%2Caps%2C104&sr=8-1