Caffeine is a xanthine alkaloid found in coffee, tea, and many other plant sources; it exhibits stimulant, bronchodilatory, anti-asthma, vasoconstrictive, anti-inflammatory, antioxidative, anti-aging, and anti-fibrotic activities. Caffeine activates adenosine receptors and inhibits phosphodiesterases (PDEs), increases levels of cAMP, activating PKA, and inhibiting the release of TNF-α and leukotrienes. In clinical settings, caffeine administration increases FEV1. Caffeine may decrease UV radiation-dependent skin damage, protecting against skin aging. Increases in caffeine consumption in human subjects are associated with decreases in risk for cardiovascular and neurological diseases. In animal models of fibrosis, caffeine decreases release of STGF, collagen I, TNF-α, IL-6, IL-1, and TGF-β1, preventing fibrosis.