The smell of leather inside cars and buses are very strong and unpleasant for some people, especially in enclosed spaces. This is caused by chemicals used in treating and preserving leather, which triggers irritation in the nose and throat. For some individuals, longer exposure may lead to symptoms such as headaches, dizziness, nausea, and even vomiting. The problem becomes worse during hot weather, as heat intensifies the smell and makes the air feel heavier and more suffocating. In crowded buses, where fresh air circulation is poor, the discomfort can increase rapidly. Many passengers find it difficult to tolerate the journey, feeling restless and uneasy. Regular exposure to such environments may also create anxiety or a conditioned response, where the mere presence of the smell leads to nausea.