{
  "id": "retinal",
  "idVersion": 1,
  "ingredient": "Retinaldehyde",
  "route": "topical",
  "grade": "moderate",
  "gradeLabel": "Moderate",
  "claim": "Two small controlled studies found retinaldehyde improved fine lines or skin elasticity versus a plain cream, with less irritation than retinoic acid.",
  "caveat": "Both controlled studies are more than 25 years old; samples were small and several secondary measurements did not improve.",
  "published": "2026-09-19",
  "sources": [
    {
      "url": "https://pubmed.ncbi.nlm.nih.gov/9843009/",
      "journal": "J Am Acad Dermatol",
      "year": 1998,
      "n": 125,
      "design": "Randomized vehicle-controlled trial",
      "duration": "44 weeks",
      "percentages": [],
      "outcome": "wrinkle profilometry, skin roughness, tolerability",
      "finding": "Randomized vehicle-controlled trial in 125 people over 44 weeks: retinaldehyde and retinoic acid improved wrinkle and roughness measures while vehicle did not; retinoic acid was more irritating than retinaldehyde.",
      "formulation": "0.05% retinaldehyde cream, 0.05% retinoic acid cream, vehicle cream"
    },
    {
      "url": "https://pubmed.ncbi.nlm.nih.gov/10473959/",
      "journal": "Dermatology",
      "year": 1999,
      "n": 40,
      "design": "Controlled study",
      "duration": "1 year",
      "percentages": [],
      "outcome": "epidermal thickness, skin elasticity, dermal thickness, skin stiffness",
      "finding": "One-year controlled study in 40 people: retinaldehyde increased epidermal thickness and elasticity versus control, while dermal thickness and stiffness did not significantly change.",
      "formulation": "0.05% retinaldehyde cream"
    }
  ],
  "peopleReport": null
}