Quick Comparison
| Hydroquinone | Tranexamic Acid | |
|---|---|---|
| Typical Concentration | OTC (where available): 2%. Prescription: 4%. Apply to dark spots only (not entire face) once or twice daily. Use in 3-4 month cycles with 2-3 month breaks. Always use with sunscreen (SPF 30+) — without it, hydroquinone is ineffective. | Topical: 2-5% in serum or cream, applied twice daily. Oral (off-label for melasma): 250 mg twice daily — requires medical supervision. Can be combined with other brightening agents. Results visible at 8-12 weeks. Especially effective for melasma. |
| Application | Topical (cream, gel, serum). Apply precisely to hyperpigmented areas. Avoid contact with normal skin. | Topical (serum, cream) or oral (tablets, off-label). Topical preferred for safety. Oral is more effective but carries systemic risks. |
| Research Papers | 9 papers | 10 papers |
| Categories |
Mechanism of Action
Hydroquinone
Hydroquinone inhibits tyrosinase through multiple mechanisms: competitive alternative substrate, oxidation to semiquinone radicals generating ROS that damage melanocyte mitochondria and ER, copper chelation at tyrosinase active site. Inhibits RNA/DNA synthesis via ribonucleotide reductase interference. Causes melanosome degradation through membrane disruption. Dramatic melanin reduction — eumelanin and pheomelanin pathways suppressed. Selectively affects hyperactive melanocytes, sparing quiescent ones. Fades pigmentation without permanently altering baseline skin color. Pigmentation returns when treatment stops (melanocyte stem cells intact). Enhanced with retinoids (penetration) and sunscreen (prevents UV rebound).
Tranexamic Acid
Tranexamic acid (TXA) is a lysine analogue that competitively inhibits plasminogen activation—binding lysine-binding sites and preventing conversion to plasmin by tPA and uPA. Plasmin normally activates multiple pathways: converts latent TGF-beta to active form, stimulates keratinocyte release of arachidonic acid and prostaglandins (PGE2, PGF2-alpha), and increases SCF and bFGF—all stimulating melanocyte proliferation and melanogenesis. By blocking plasmin, TXA interrupts this paracrine cascade, reducing melanin through a mechanism independent of tyrosinase. TXA also inhibits VEGF and reduces angiogenesis—addressing melasma's vascular component. May reduce UV-induced plasmin in keratinocytes. This unique mechanism makes TXA synergistic with tyrosinase inhibitors for stubborn melasma.
Risks & Safety
Hydroquinone
Common
Mild redness, stinging, dryness.
Serious
Exogenous ochronosis (paradoxical blue-grey darkening) with prolonged use >6 months, particularly in darker skin tones. Irritant and allergic contact dermatitis.
Rare
Nail discoloration, peripheral neuropathy (extremely rare, systemic exposure).
Tranexamic Acid
Rare
Topical form has minimal systemic absorption and low risk.
Full Profiles
Hydroquinone →
The most potent topical depigmenting agent available and the gold standard prescription treatment for melasma and stubborn hyperpigmentation. Hydroquinone inhibits tyrosinase more strongly than any OTC alternative. However, it carries risks with long-term use (ochronosis — paradoxical darkening) and is restricted or banned in many countries. Best used in cycles of 3-4 months under dermatologist guidance.
Tranexamic Acid →
Originally an oral medication for heavy menstrual bleeding, tranexamic acid (TXA) has emerged as one of the most effective treatments for melasma and stubborn hyperpigmentation that does not respond to conventional treatments. It works through a unique mechanism — blocking plasmin-mediated stimulation of melanocytes — that is different from tyrosinase inhibitors, making it an excellent combination partner.