The weather is warm, but your throat is sore, you have a headache, your nose and chest are congested, and you're tired — it's a summer cold. What potentially happens next is a sinus infection, and with that a more complex set of problems for aviators. Even with antibiotics, the symptoms — which can reappear at altitude even though the pain may have subsided — can last for several days. A cold is proper cause for temporarily grounding yourself from flying. Don't risk impairing your performance and decision-making abilities by flying after taking unapproved over-the-counter medications.