Avoid if narrow angl. Only a narrow occludable angle without a patent laser iridotomy is at risk for pupillary block angle closure induced by otc cold meds. A narrow angle needs to be found preventatively on gonioscopy exam in the office.
OTC. Most over the counter (otc) cold remedies are ok - just beware of those containing pseudo Ephedrine (ephedrine sulfate) as this may increase BP and also potentially the pressure in the narrow angle glaucoma -- some rare allergy to the most common antihistamine (diphenhyramine or benadryl) occurs that may cause increase pulse and blood pressure.
It depends. If he has closable angle glaucoma then he should be treated with laser and cured. Otherwise he should avoid medications that can dilate his pupils such as antihistamines.
Meds in glaucoma. All drugs, over the counter or prescription, have in the package insert a legally ordered disclaimer: "do not use if you have glaucoma". If you have ordinary glaucoma, you can ignore this. If you know you have angle closure potential (uncommon) you have probably already had this treated. So over all you can ignore this warning.
Angle closure risk. Angle closure glaucoma is rare but not everyone who has the potential for this condition has been treated, or even knows that they have it. Ask your father if he has open angle glaucoma, and then the most common cold medicines are safe to use. Generally avoid one with decongestants if you are on certain types of blood pressure meds, your family doctor can advise you if this is an issue.
Fluids/tylenol. Non-sedating antihistamine: avoid all decongestant and decongestant cough medications since they can raise your BP. I suggest zinc losenges (Cold-Eze) and dark brown honey, hot steam showers and force the fluids.
Avoid decongestants. Decongestant OTC cold remedies cause the most concern. Avoid products that contain pseudoephedrine, (ephedrine sulfate) ephedrine, (ephedrine sulfate) phenylephrine, naphazoline and oxymetazoline. Look for labels which indicate "safe for hypertension" patients. Simple acetominophen may help, as will a saline nasal spray. Gargle with warm salt water or drink warm water with lemon and honey. Stay hydrated. Increase home humidity. REST!