We have a shih 'tzu dog and a siamese cat. Although shih 'tzu's don't really shed and have to be groomed, they still have dander. We switched from the basic, inexpensive furnace filter to the Filtrete Allergen Reduction filter when our son started showing symptoms of allergies. We feel better knowing this filter can trap smaller particles that could cause breathing problems, especially while he sleeps. Our dog is all over the house, so we know he could be distributing dander everywhere. But our cat sleeps most of the day, so we don't think he contributes much to poor air quality, except when he uses the litter box. When the Filtrete filter is removed, it's easy to see what it has trapped, because the media is gray, compared to the pure white of a new one. What a great feeling to know those particles are stuck to the Filtrete filter and not inside our family's lungs.
The 3M 4" Filtrete Filter is a quality product. It calls for a change every 6 months to a year. It does pick up quite a bit of traffic after 6 months, so we change it. The only issue is the cost. I guess you pay for what you get.