A+ High-Dose Retinoid Serum
Gentle Retinoid for Beginners
Verified reviewer
Pros & cons.
- +Dual retinoid system with HPR for immediate activity and liposomal retinol for sustained release
- +Notably gentler adjustment period than most traditional retinol serums
- +Dense soothing support with bisabolol, prickly pear, ginger, honey, and CoQ10
- +Lightweight texture absorbs quickly and layers well under moisturizer
- +Fragrance-free formulation despite the brand's prestige positioning
- +Airless pump packaging protects unstable retinoid actives from degradation
- +Effective entry point for people new to retinoid therapy
- −The 6.5% retinoid claim conflates ingredients of vastly different potencies
- −At $85 per ounce the price is steep for 0.5% HPR concentration
- −Unpleasant chemical smell described as old rubber by multiple reviewers
- −Brand's FTC fake review settlement raises questions about early consumer feedback
- −Contains alcohol (listed low in INCI but present)
The full review.
The headline number is 6.5%. It dominates the marketing, and in a market where consumers track concentrations, it sounds potent. But the math tells a different story.
The 6.5% includes three parts: 5% retinoid esters (gentle vitamin A derivatives requiring multiple enzymatic conversion steps to become active), 1% liposome-encapsulated retinol blend (traditional retinol in a slow-release delivery system), and 0.5% blue-green algae extract with retinoid-like activity. The most important ingredient — Hydroxypinacolone Retinoate, the ‘high-dose retinoid’ in the product name — is only about 0.5%. This is not a criticism; 0.5% HPR is meaningful because of its direct receptor-binding activity. However, the 6.5% figure totals ingredients with vastly different potencies, much like adding a bicycle’s horsepower to a car’s.
Setting marketing aside, the formulation is interesting. Sunday Riley’s founder is a trained cosmetic chemist, and the dual retinoid approach shows sophistication. HPR — Hydroxypinacolone Retinoate — is a retinoic acid ester that binds directly to retinoid receptors. It skips the multi-step enzymatic conversion that retinol requires. Retinol must convert to retinaldehyde, then to retinoic acid, to activate receptors. In vitro research shows HPR stimulates procollagen production at levels comparable to tretinoin, with less inflammatory response.
The second component — liposome-encapsulated retinol — uses a sustained-release mechanism. Phospholipid liposomes act as delivery vehicles, slowly releasing retinol into the skin over hours instead of all at once. This time-release approach reduces the irritation spike from free retinol and extends retinoid activity. The formula delivers benefits through two pathways: HPR for immediate receptor activation and liposomal retinol for sustained, conversion-dependent activity.
The other ingredients form a soothing protocol to make this retinoid therapy tolerable. Bisabolol (chamomile-derived), prickly pear fruit extract, ginger root extract, honey extract, and CoQ10 provide anti-inflammatory and antioxidant support. Sodium hyaluronate crosspolymer hydrates longer than standard hyaluronic acid. Cetylhydroxyproline palmitamide acts as a ceramide-like barrier support. Shea butter adds emollience. This formula does not just apply retinoids; it actively manages the irritation retinoid therapy often produces.
Texture
The texture is a lightweight, slightly yellow-tinted lotion that absorbs quickly and feels weightless. One to two pumps cover the full face. It layers well under a heavier moisturizer or facial oil, which is how most retinoid serums should be used, especially during the adjustment period.
Scent
The smell varies by user. Reviewers describe it as ‘old rubber,’ ‘chemical,’ or ‘weird.’ The product is fragrance-free, but the combination of HPR, retinol, and the Dimethyl Isosorbide penetration enhancer produces an odor some find off-putting. It dissipates within minutes. Sunday Riley chose not to mask it with added fragrance, which is a positive sign, but users should expect it.
Common Praise
Most users report visible improvements in skin smoothness and radiance within two to four weeks. More significant changes in fine lines and dark spots emerge over eight to twelve weeks. The adjustment period — mild flaking, possible tightness, or occasional purging — is gentler than many traditional retinol products. This is the goal of the HPR-forward approach. Retinoid beginners often use this as a manageable entry point into vitamin A therapy.
Common Complaints
In 2020, the FTC issued a consent agreement after finding Sunday Riley directed employees to post fake positive reviews on Sephora between 2015 and 2017. While the A+ launched in 2019 — after the fake review period — the scandal raises questions about the brand’s relationship with honest feedback. The brand still operates at major retailers, and the consent agreement prohibited future deceptive practices, but consumers should know this context.
Value
The value is simple: $85 for one ounce of a serum where the star active is 0.5% is expensive. The formulation is sophisticated, the delivery technology is thoughtful, and the soothing support is generous. However, you pay prestige prices, and other HPR-based products cost significantly less. Whether Sunday Riley’s specific approach (dual retinoid, heavy soothing support, airless pump stability) justifies the premium over a simpler HPR serum at half the price is a personal choice.
Best for
The A+ makes retinoid therapy accessible to people who find it intimidating. The gentle adjustment period, lightweight texture, buffered delivery systems, and soothing botanicals remove barriers to consistent use. It is designed for those who stopped using retinol due to irritation, or those nervous about starting retinoids. Whether that approachability is worth $85 depends on your priorities.
Formula
Ingredient analysis.
Full INCI list
Water/Eau/Aqua, Dimethyl Isosorbide, Propanediol, Triheptanoin, Dimethicone, Glycerin, Pentylene Glycol, Cetyl PEG/PPG-10/1 Dimethicone, Disiloxane, Hexyldecanol, Diheptyl Succinate, Propylene Carbonate, Phenyl Trimethicone, PPG-24-Glycereth-24, Hydroxypinacolone Retinoate, Sodium Acrylates Copolymer, Helianthus Annuus (Sunflower) Seed Oil, Honey Extract, Opuntia Ficus-Indica Fruit Extract, Bisabolol, Butyrospermum Parkii (Shea) Butter, Retinol, Sodium Hyaluronate Crosspolymer, Ubiquinone, Zingiber Officinale (Ginger) Root Extract, Tocopherol, Hydrogenated Polydecene, Lecithin, 1,2-Hexanediol, 4-T-Butylcyclohexanol, Caprylyl Glycol, Phospholipids, Polyglyceryl-10 Stearate, Sorbitol, Cetylhydroxyproline Palmitamide, Polysilicone-11, Benzoic Acid, Dehydroacetic Acid, Capryloyl Glycerin/Sebacic Acid Copolymer, Sodium Phytate, Phenoxyethanol, Glyceryl Polyacrylate, Alcohol, Polysorbate 20, Saccharomyces Cerevisiae Extract, Brassica Campestris (Rapeseed) Sterols
Skin match.
The science.
The Science
Hydroxypinacolone Retinoate (HPR) represents a newer approach to retinoid therapy that has generated genuine scientific interest. Unlike retinol, which must undergo a two-step enzymatic conversion (retinol → retinaldehyde → retinoic acid) before it can activate retinoid receptors, HPR is a retinoic acid ester that binds directly to retinoid acid receptors (RAR). This direct binding means it's pharmacologically active upon contact with skin cells, without depending on the conversion enzymes whose expression varies between individuals.
A 2018 study by Ruth and Mammone presented at the Journal of Investigative Dermatology found that HPR increased procollagen production in skin models at levels comparable to all-trans retinoic acid (tretinoin) — the gold standard prescription retinoid — without inducing the heightened inflammatory response that tretinoin produces. At the highest tested dose, HPR actually outperformed tretinoin in collagen staining metrics. The researchers concluded HPR is 'an effective alternative to ATRA and other less potent retinoids without the detrimental side-effects.'
A 2023 clinical trial by Wang et al. published in the Journal of Cosmetic Dermatology studied 42 women using HPR combined with retinyl propionate over 8 weeks. The combination reduced wrinkles by 8.3%, improved smoothness by 11.9%, decreased transepidermal water loss by 25.7%, and improved elasticity by 14.5-22.6% — with no adverse reactions reported. These results support the multi-retinoid approach used in the A+ formula.
More recently, a 2025 study by Shen et al. published in the Journal of Cosmetic Dermatology examined an HPR + retinol combination serum in 31 women over 8 weeks. The combination activated TGF-beta/Smad signaling pathways — key molecular cascades in collagen production — with a gene expression profile that more closely resembled HPR's activity than retinol's alone, suggesting HPR is the dominant driver of anti-aging effects even when combined with retinol.
The liposomal delivery of retinol in this formula uses phospholipid encapsulation to create a sustained-release mechanism. Research on liposomal retinol delivery has consistently shown reduced irritation potential compared to free retinol at equivalent concentrations, with comparable or improved efficacy due to the more gradual release profile.
References
- Anti-aging effects of retinoid hydroxypinacolone retinoate on skin models — Journal of Investigative Dermatology (2018)
- The synergistic effect of retinyl propionate and hydroxypinacolone retinoate on skin aging — Journal of Cosmetic Dermatology (2023)
- An Innovative Serum With Retinol, Hydroxypinacolone Retinoate, Peptides, and Silybin Improves Mild Photoaged Facial Skin — Journal of Cosmetic Dermatology (2025)
Dermatologist Perspective
Board-certified dermatologists recognize HPR as a promising retinoid with a growing evidence base, though most note that the published research is still far smaller than the decades of clinical data supporting tretinoin and retinol. Dermatologists frequently recommend the A+ as a stepping stone for patients who find prescription retinoids intolerable — the gentler adjustment period can help build compliance before transitioning to stronger retinoid therapy if needed. The dual retinoid approach is viewed favorably from a formulation standpoint, and the dense soothing support addresses one of the most common reasons patients abandon retinoid therapy. However, dermatologists also note that the prestige price point puts this product in competition with prescription tretinoin, which is both more potent and often less expensive with insurance coverage.
Where it fits in your routine.
Apply 1-2 pumps to clean, dry skin every other evening. If skin tolerates it after 2-4 weeks, use it nightly. Follow with a moisturizer containing ceramides or thick emollients to support the skin barrier during retinoid adjustment. Always apply broad-spectrum SPF 30+ the next morning because retinoids increase photosensitivity. Do not use AHA/BHA exfoliants or benzoyl peroxide on the same nights you use this serum.
At $85 for 1 ounce, the A+ costs more than most over-the-counter retinoid serums. The 0.5 oz size at $50 allows for cheaper trial, while the 1.7 oz size at $122 ($71.76/oz) gives the best value for regular users. The formulation is more sophisticated than most retinol products; the dual retinoid system, liposomal delivery, and soothing support show real R&D investment. However, HPR-based products from other brands use similar active technology for much less. The premium comes from formulation complexity and the Sunday Riley brand name. For retinoid beginners who prioritize tolerability, the price fits the gentler experience. For experienced retinoid users who tolerate irritation, cheaper, more potent options exist.
Retinoid beginners and people with a history of retinol intolerance can start vitamin A therapy with minimal irritation. It also works for anyone seeking a premium anti-aging treatment for fine lines, dullness, and hyperpigmentation without the harsh adjustment period of traditional retinol products.
Budget-conscious shoppers can buy HPR and retinol products for much less. Users comfortable with prescription tretinoin or high-percentage retinol serums gain no extra benefit to justify the cost. Pregnant and breastfeeding individuals avoid all retinoid products.
Product details.
All Year
The backstory.
Launched in January 2019, the A+ was Sunday Riley's answer to the retinoid renaissance that was sweeping the prestige skincare market. The brand's founder — a cosmetic chemist by training — built the formula around Hydroxypinacolone Retinoate, a retinoic acid ester that had been generating excitement in dermatological research for its ability to deliver retinoid benefits with less irritation. The 'A+' name signals both the vitamin A ingredient class and the ambition to be a top-of-class retinoid treatment.
About Sunday Riley
Established Brand (5–20 years)Cosmetic chemist Sunday Riley founded Sunday Riley in 2009 in Houston, Texas. The brand is a top independently owned prestige skincare line in America and sells at Sephora, Ulta, and Nordstrom. However, the FTC issued a consent agreement in 2020 after finding the company told employees to post fake positive reviews on Sephora between 2015-2017. This finding questions the authenticity of the brand's early review data.
Common myths.
The 6.5% concentration makes this a strong retinoid product.
The 6.5% figure totals all retinoid and retinoid-like ingredients, including gentle esters and a blue-green algae extract. The most potent active, HPR, is 0.5%, and the retinol concentration in the liposomal blend is undisclosed. Many drugstore retinol products contain 0.3-1% pure retinol. While the 6.5% figure is technically accurate, it can overstate the product's potency.
HPR is as effective as prescription tretinoin.
In vitro studies show HPR stimulates procollagen production like tretinoin, but head-to-head human clinical trials at comparable concentrations are limited. HPR is promising and less irritating, but the evidence base is smaller than the decades of research for tretinoin. It is a gentler alternative, not a proven equivalent.
FAQ.
Is the Sunday Riley A+ serum really 6.5% retinoid?
The 6.5% total includes 5% retinoid esters, 1% liposome-encapsulated retinol blend, and 0.5% blue-green algae extract with retinoid-like activity. The most potent ingredient — Hydroxypinacolone Retinoate (HPR) — is about 0.5%. This total is accurate but makes the product seem more intense than a straight retinol percentage.
Can I use the Sunday Riley A+ if I've never used retinol before?
Yes — this is a top retinoid serum for beginners. The HPR is gentler than traditional retinol. The formula contains soothing agents like bisabolol, prickly pear, honey, and CoQ10. Use 1-2 pumps every other night and layer a thick moisturizer on top. Move to nightly use over 2-4 weeks as your skin adjusts.
Why does the Sunday Riley A+ smell so bad?
The unusual chemical or "old rubber" smell comes from the active ingredients—mainly HPR and retinol—and the Dimethyl Isosorbide solvent used to increase penetration. The formula has no added fragrance. The smell disappears minutes after application. This is the trade-off for a fragrance-free formulation that supports skin health.
Can I use vitamin C with the Sunday Riley A+ retinoid?
Yes, but in separate routines. Use your vitamin C serum in the morning and the A+ retinoid serum at night. Using them together reduces the efficacy of both ingredients and increases irritation. This morning/evening split works best.
Is the Sunday Riley A+ worth the price?
The formulation is sophisticated. The dual retinoid system uses HPR and liposomal retinol, and the soothing ingredients are plentiful. However, at $85 for 1 oz, the HPR concentration is only 0.5%, and several competitors sell HPR-based retinoid serums for less. Value depends on whether you prioritize the specific formulation approach or the active concentration alone.
Is the Sunday Riley A+ safe during pregnancy?
No. This product contains retinol and Hydroxypinacolone Retinoate, both vitamin A derivatives. Avoid all topical retinoids during pregnancy and breastfeeding because vitamin A carries a theoretical risk of birth defects. Ask your healthcare provider for pregnancy-safe alternatives.
What the community says.
"Noticeably smoother and firmer skin within 2-4 weeks of consistent use"
"Significantly gentler than traditional retinol serums with minimal irritation"
"Lightweight lotion texture absorbs quickly without heaviness"
"Visible improvement in radiance and overall skin glow"
"Effective for retinoid beginners who can build tolerance gradually"
"Unusual chemical smell frequently described as old rubber or medicinal"
"High price relative to the actual HPR concentration of only 0.5%"
"The 6.5% total retinoid claim includes weaker esters — potentially misleading"
"Some users still experience purging and flaking during adjustment"
"Price-to-potency ratio questioned versus more affordable HPR alternatives"
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