Hello. Welcome to Ask A Doctor . I have read your query and here is my advice. A side effect of Motrin(ibuprofen) is to cause stomach inflammation which can make the stomach s inside lining bleed. The blood is carried along with intestinal contents through the entire intestinal tract. By the time it reaches the end it is black and makes stool black. Blueberries, Pepto-Bismol, and iron supplements also make stool black. A hive rash is an allergic rash and could be due to Motrin, especially if the hives appeared very soon after you gave him the dose. Tylenol does not irritate the stomach and is safer. Hard stool is usually due to not enough liquid intake. You may want to try giving apple and pear juices. If that doesn t help, prune juice, 1-2ounces one-two times per day might be beneficial. Frequent colds and coughing could be from being in close contact with other young children who are infected with various viruses. How old is your child? Does he attend daycare? Also, cold and cough syrups are NOT recommended to give to children five years or under because their is no evidence that they are effective for colds and they have side effects. Saline nose drops(such as Nasal) one drop into each nostril before feeding and naptime will moisturize his nasal mucus and help him to sneeze and blow mucus to front of nose where you can easily suction it out. Humidifier so that mist gets to his nose might also help. Hope I have answered your query. If you have any further questions, I will be happy to help. Arnold Zedd, MD, FAAP