p-phenylenediamine (PPD) is a common component of hair dye known to induce immediate allergy, even acute dermatitis and contact dermatitis. MAS-related G protein coupled receptor-X2 (MRGPRX2) in mast cells (MCs) mediates small molecular substances-induced pseudo-allergic reactions. However, the role of MRGPRX2 in PPD-induced immediate contact allergy needs further exploration. The aim of this study was to investigate whether PPD activates MCs via MRGPRX2 and induces immediate allergies that contribute to contact dermatitis. Wild-type (WT) and kit^w-sh/w-sh mice (MUT) were treated with PPD to observe local inflammation and MC degranulation in vivo. The release of inflammatory mediators was measured in vitro. Histamine 1 receptor (H₁R)^−/− mice were used to analyze itch type. PPD caused immediate contact allergy in WT mice, induced scratching, and local inflammatory reactions, while exhibiting minimal effects on MUT mice. PPD did not induce histamine release, but induced significant tryptase release in vivo and in vitro. PPD activated MRGPRX2 to induce MC degranulation in vitro. PPD caused immediate contact allergy in WT mice, induced scratching and local inflammatory reactions, while exhibited minimal effect on MUT mice. PPD did not induce histamine release, while induced significant tryptase release in vivo and in vitro. PPD induced immediate contact allergy by MCs activation via MRGPRX2 and lead to tryptase release. The scratching times showed no significant difference in WT mice or H₁R^−/- mice, which indicated PPD caused non-histaminergic itch. The results showed that PPD activated MCs via MRGPRX2 and induced immediate contact allergy, leading to the release of tryptase without monoamine release, which might induce non-histaminergic itch.

对苯二胺 (PPD) 是染发剂的常见成分，已知会引起立即过敏，甚至引起急性皮炎和接触性皮炎。肥大细胞 (MC) 中 MAS 相关的 G 蛋白偶联受体 -X2 (MRGPRX2) 介导小分子物质诱导的假过敏反应。然而，MRGPRX2 在 PPD 引起的直接接触过敏中的作用需要进一步探索。本研究的目的是调查 PPD 是否通过 MRGPRX2 激活 MC，并诱发直接过敏，从而导致接触性皮炎。野生型（WT）和试剂盒^w-sh/w-sh小鼠（MUT）用PPD处理，观察体内局部炎症和MC脱粒情况。体外测量炎症介质的释放。使用组胺 1 受体 (H ₁ R) ^−/−小鼠来分析瘙痒类型。 PPD 在 WT 小鼠中引起直接接触过敏，诱发抓挠和局部炎症反应，而对 MUT 小鼠的影响很小。 PPD 不诱导组胺释放，但在体内和体外诱导显着的类胰蛋白酶释放。 PPD激活MRGPRX2以在体外诱导MC脱颗粒。 PPD 在 WT 小鼠中引起直接接触过敏，诱导抓伤和局部炎症反应，而对 MUT 小鼠的影响最小。 PPD不诱导组胺释放，但在体内和体外诱导显着的类胰蛋白酶释放。 PPD 通过 MRGPRX2 激活 MCs 诱导立即接触过敏，并导致类胰蛋白酶释放。 WT小鼠和H ₁ R ^-/-小鼠的抓挠时间没有显着差异，这表明PPD引起非组胺能瘙痒。 结果表明，PPD通过MRGPRX2激活MC并诱导立即接触过敏，导致类胰蛋白酶释放而不释放单胺，这可能诱发非组胺能瘙痒。