Hi, Alka Seltzer is used for relief of stomachache, acid reflux, indigestion, heartburn, upset stomach, fever, mild painful conditions etc. Side effects of Alka Seltzer are nausea, vomiting, increased thirst, headache, difficulty in swallowing, loss of appetite, vomiting of blood, bloody or black tarry stools, muscle pain, ringing in the ears, unpleasant taste, usual tiredness or weakness, mood swings, bloody urine, rashes, itching, swelling of face, fingers, ankles, feet or lower legs, dizziness, difficulties in breathing etc. Before start taking Alka Seltzer, you should consult your doctor first. You should not use this medication without your doctor s advice. Baking powder is a dry chemical and a mixture of carbonate or bicarbonate that is used for increasing the volume as well as lightening the texture of baked goods. Long term and overuse of baking soda may cause side effects such as nausea, vomiting, stomach pain, thirst, excess gas, headache, frequent urination, fatigue, diarrhea, muscle weakness and cramps, increased stomach acid production, electrolytes imbalance, allergic reactions etc. Take care. Hope I have answered your question question. Let me know if I can assist you further. Regards, Dr. Zubayer Alam, General And Family Physician