Allergic diseases are common in women of childbearing age. Both asthma and atopic conditions may worsen, improve or remain the same during pregnancy. Primary care physicians commonly encounter women receiving multiple medications for pre-existing atopic conditions, who then become pregnant and require medication changes to avoid potential fetal injury or congenital malformations. Each medication should be evaluated; intranasal and inhaled steroids are relatively safe to continue during pregnancy (budesonide is the drug of choice), second-generation antihistamines of choice are cetirizine and loratadine, leukotriene receptor antagonists are safe, sparing use of oral decongestants during the first trimester and omalizumab may be used for both uncontrolled asthma and for antihistamine-resistant urticaria. Medications to avoid during pregnancy include intranasal antihistamines, first-generation antihistamines, mycophenolate mofetil, methotrexate, cyclosporine, azathioprine and zilueton. Common allergic diseases may develop de novo during pregnancy, such as anaphylaxis.