Quercetin

Quercetin is a naturally occurring flavonoid antioxidant found in foods such as onions, apples, berries and leafy vegetables. It is commonly used in supplements to support antioxidant defence, immune function and a healthy inflammatory response.

Quercetin is also well known for its relationship with histamine and mast-cell activity, which makes it especially relevant to seasonal and allergy-support formulas.

Antioxidant and Cellular Support

Quercetin helps protect cells from oxidative stress by neutralising reactive molecules and supporting the body’s wider antioxidant systems.

This gives it a broad role in formulas for immune resilience, healthy ageing and cellular protection, particularly during periods of environmental or metabolic stress.

Seasonal and Histamine Support

One of quercetin’s most distinctive uses is in formulas aimed at seasonal sensitivities.

Quercetin can help support normal mast-cell stability and histamine regulation, which is why it is often included in products designed to support the body during exposure to pollen and other environmental triggers.

It is frequently paired with nutrients such as vitamin C, zinc and bromelain for broader seasonal support.

Inflammatory Balance

Quercetin also influences several pathways involved in the body’s normal inflammatory response.

This makes it useful beyond seasonal support, including formulas aimed at joint health, recovery and general resilience.

Quercetin and Bioavailability

Quercetin is not always absorbed efficiently on its own.

For this reason, it is often combined with ingredients such as bromelain or BioPerine®, which may help improve absorption or complement its activity within multi-ingredient formulas.

Quercetin for Pets

Quercetin can also be included in supplements for dogs and cats, particularly in formulas for seasonal sensitivities, skin health, immune support and antioxidant protection.

It is commonly paired with ingredients such as bromelain, omega-3 fatty acids, vitamin C and other antioxidants to provide broader support for normal inflammatory and histamine responses.

Quercetin in O2B Products

At O2B Healthy, quercetin is used in O2B Quercetin Plus and O2B Allerg-eze for immune, antioxidant and seasonal allergy support, as well as O2B MitoCell+ for broader cellular and healthy-ageing support. It is also included in our O2B K9+ Allergies formulas for small, medium, large and extra-large dogs. Across these products, quercetin complements ingredients such as vitamin C, bromelain, MSM, NAC and zinc to support healthy histamine responses, antioxidant defence, immune function and normal inflammatory balance.