Dr. Patel explained that cat allergies aren't caused by cat hair. Most people don't know this and most doctors don't explain it, because the treatment protocol is the same either way.
The real cause is a specific protein called Fel d 1.
It's produced in cat saliva and skin glands. When Miso grooms herself which she does for hours every day she coats every hair on her body with this protein. It dries. It becomes microscopic. It floats.
And here is the part that explained everything:
Fel d 1 particles are extraordinarily small. Smaller than most airborne allergens. Small enough to stay suspended in the air for hours. Small enough to pass through most standard filters.
And because they're sticky, they embed themselves into every soft surface in the home — the sofa, the bedding, the curtains, the carpet. Even the HVAC system carries them from room to room.
This is what "allergen load" means. It's the total concentration of Fel d 1 in your home environment.
And here is why this matters for allergy shots:
"Immunotherapy builds tolerance gradually. But tolerance has a ceiling. If someone's daily allergen load is very high, their immune system can be stimulated faster than the shots can build resistance. The load overwhelms the therapy."
Craig's shots were working. His body was slowly building tolerance.
But every day, he was going home and breathing in so much Fel d 1 that the tolerance couldn't keep up.
The air purifiers we'd bought? Fel d 1 particles are often too small to be reliably captured by standard HEPA filtration. They pass through and keep circulating.
The antihistamines he took on bad days? Masking the reaction to a protein that was still present at full concentration.
The bedroom we'd banned Miso from for eight months? Still saturated with Fel d 1 that had accumulated before the ban and never been neutralized.
We had been trying to empty the glass while someone kept refilling it.