Self-treatment for allergies with over-the-counter medications may lead to unwanted side effects, such as drowsiness and fatigue. Some remedies may worsen the underlying condition. Untreated allergies often are found to be the source of other serious conditions, such as asthma and sinus or ear infections. Other medical conditions that can cause or aggravate asthma include chronic sinusitis, acid reflux and sleep apnea. If these conditions are suspected, further testing and treatment may be needed to optimize treatment and outcomes.