Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat. Although not all side effects are known, chondroitin and glucosamine is thought to be possibly safe when taken for up to 2 years. Stop using chondroitin and glucosamine and call your healthcare provider at once if you have: irregular heartbeats; or swelling in your legs. Common side effects may include: nausea, diarrhea, constipation; stomach pain, gas, bloating; hair loss; or puffy eyelids. This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.