Both antacids and antiallergic drugs are antihistamines but they cannot replace each other. Explain why ?

Explanation

### Step-by-Step Solution:

1. **Definition of Antacids and Antihistamines**:
- Antacids are substances that neutralize stomach acidity. They are primarily used to relieve symptoms of heartburn and indigestion caused by excess stomach acid.
- Antihistamines, on the other hand, are drugs that block the action of histamine, a chemical in the body that is involved in allergic reactions.

2. **Function of Antacids**:
- Antacids work by increasing the pH level in the stomach. They contain basic compounds such as sodium bicarbonate or magnesium hydroxide. When ingested, they neutralize excess hydrochloric acid in the stomach, providing relief from acidity.
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