…you feel like you might be getting a cold (congestion, headachy, coughing, tired). Do you drink tea and put your feet up? No, you spend Sunday dusting and vacuuming the bedroom, changing the sheets and mattress cover, running the pillows and comforter through the hottest dryer setting to kill dust mites, washing your CPAP mask and hose, swapping in a clean CPAP filter, and otherwise doing your best to minimize allergens. Oh, and some cleaning in the rest of the house (vacuuming, dusting, etc).
Because if it’s allergies, and not a cold? This may alleviate (or at least help) the problem.
And if it’s a cold, and not allergies? Doing allergen-patrol while you still feel up to it will help keep the cold from being compounded by allergies later.