**Core Concept**
Oxygen therapy is a treatment that delivers a higher concentration of oxygen to a patient, typically through a mask or nasal cannula. The goal is to increase oxygen levels in the blood to alleviate hypoxia. However, oxygen therapy can have side effects due to the potential for oxygen toxicity.

**Why the Correct Answer is Right**
The side effects of oxygen therapy occur because oxygen is a pro-oxidant that can react with biological molecules, leading to tissue damage. This is especially true at high concentrations, such as above 60% FiO2. The primary concern is the formation of reactive oxygen species (ROS), which can damage cellular components, including DNA, proteins, and lipids.

**Why Each Wrong Option is Incorrect**
**Option A:** Oxygen toxicity is a known side effect of oxygen therapy. It can cause convulsions, lung damage, and even death.
**Option B:** Oxygen therapy can also cause dryness and irritation of the nasal passages and throat due to the increased concentration of oxygen.
**Option C:** Oxygen therapy is not typically associated with anaphylaxis, which is a severe, life-threatening allergic reaction.

**Clinical Pearl / High-Yield Fact**
It's essential to monitor patients receiving oxygen therapy for signs of oxygen toxicity, such as seizures or lung damage. The FiO2 should be titrated to the lowest effective level to minimize the risk of side effects.

**Correct Answer:** A. Oxygen toxicity is a known side effect of oxygen therapy.