A healthy liver creates antibodies which attack allergens. However, when its functioning decreases, the body stores those allergens. The brain responds by producing histamine, a chemical which marks the allergens for removal. Excessive buildup of histamine leads to allergy symptoms like itchiness, fogginess, and headaches.
Toxins prevent the metabolism of muscle tissues, which results in ache and physical fatigue. With time, the tiredness can turn into moodiness, depression, and angry outbursts.