Yes, sinus infections (sinusitis) can be caused or worsened by allergies. When you have an allergic reaction to environmental triggers such as pollen, dust mites, pet dander, or mold, your immune system releases chemicals like histamine, which causes inflammation in the nasal passages and sinuses. This inflammation can block sinus drainage, leading to mucus buildup, and can create a favorable environment for bacteria to grow, resulting in a sinus infection.

How Allergies Contribute to Sinus Infections:
Inflammation of the Nasal Passages: Allergies cause swelling and irritation of the nasal passages, which can block the sinus openings.
Increased Mucus Production: Allergic reactions often increase mucus production, which can accumulate in the sinuses and contribute to infection.
Sinus Blockage: Swollen nasal tissues and excess mucus can prevent proper drainage of the sinuses, creating a breeding ground for bacteria or viruses.
How to Treat Allergic Sinus Infections:
Allergy Medications:

Antihistamines: These help reduce the allergic response and prevent symptoms like nasal congestion and runny nose. Common over-the-counter options include cetirizine (Zyrtec), loratadine (Claritin), and fexofenadine (Allegra).
Nasal Corticosteroids: These reduce inflammation in the nasal passages and sinuses, helping to open up the sinuses and reduce symptoms. Examples include fluticasone (Flonase) and budesonide (Rhinocort).
Decongestants: Oral or nasal decongestants (e.g., pseudoephedrine or phenylephrine) can reduce nasal swelling and help with sinus drainage. However, nasal decongestants should not be used for more than 3 consecutive days to avoid rebound congestion.
Nasal Irrigation:

Saline Nasal Sprays or Rinses: Using a saline solution (e.g., Neti pot) can help clear out mucus, allergens, and irritants from the nasal passages and sinuses, reducing congestion and inflammation.
Avoiding Allergens:

Identify and Minimize Exposure: Identifying the allergens causing your reactions and reducing exposure can help prevent allergic sinus infections. For example, keeping windows closed during high pollen seasons or using air purifiers in your home.
Washing Bedding and Clothes: Regularly washing sheets, pillowcases, and clothes in hot water can help remove allergens like dust mites and pet dander.
Managing Seasonal Allergies:

If your allergies are seasonal (e.g., due to pollen), consider starting allergy treatments before the allergy season begins to prevent sinus problems.
Immunotherapy (Allergy Shots):

For people with persistent allergies, allergy shots (immunotherapy) can help desensitize the immune system to specific allergens, providing long-term relief and potentially preventing allergic sinus infections.
Antibiotics (If Bacterial Infection Develops):

If a sinus infection becomes bacterial due to allergies, your doctor may prescribe antibiotics. This is more likely if symptoms persist for more than 10 days or worsen despite treatment for allergies.
Hydration:

Drinking plenty of fluids can help thin mucus, making it easier for the sinuses to drain.
Conclusion:
Allergic sinus infections can be managed effectively with allergy treatments, nasal irrigation, and avoiding allergens. If symptoms persist or if you suspect a bacterial infection, it's important to consult a healthcare provider for further treatment options.