Since his symptoms have lasted for a month, it is important to have him evaluated by a doctor. A typical cold usually resolves within ten days; a prolonged cough could indicate allergies, post-nasal drip, or asthma rather than a simple infection. For temporary relief, he can try saline nasal sprays, steam inhalation, or an over-the-counter antihistamine like cetirizine. Please avoid taking antibiotics without a prescription, as they will not help unless a bacterial infection is diagnosed. A healthcare provider can safely listen to his chest and prescribe the correct, targeted treatment.