Neutrogena® Hydro Boost City Shield™ Water Gel Sunscreen Broad Spectrum SPF 25

DESCRIPTION

What It Does: Provides uva-i protection (340-400nm) critical for photoaging prevention — the only widely available chemical uva-i filter.

Why It's Used: The essential uva-i filter — avobenzone is the only commonly approved chemical filter providing protection in the photoaging-critical 340-400nm range essential for broad-spectrum sunscreen claims.

How It Works: Dibenzoylmethane chromophore absorbs uva-i (λmax 357nm, εmax ~36,000). photodegrades via photoisomerisation requiring photostabilisation (octocrylene, bemotrizinol) for durability.

Typically Found In: Broad-spectrum sunscreens,anti-aging spf products

TECHNICAL DETAILS

Primary Category: Active ingredient – chemical uva-i filter

Secondary Functions: Skin conditioning

Application Areas:

Facial Skincare

Body Care

Hair Care

Beard Care

Color Cosmetics (Makeup)

Dietary/Oral Supplements

Typical Concentration Range: Up to 5% (eu), 3% (us fda)

SOURCING & ETHICS

Vegan Status: Yes – synthetic

Halal Status: Yes

Source Notes: Commercially produced for cosmetic use. verify vegan/halal status with supplier.

SKIN COMPATIBILITY

Irritancy Rating: 1/5 – very low

Comedogenicity Rating: 0/5 – non-comedogenic

Sensitivity Concerns: Well-tolerated by most skin types.

Safe for Sensitive Skin: Yes

SAFETY & COMPATIBILITY

Safety Profile: Eu max 5%. fda: 3%. ewg score: 2. requires photostabilisation. photoallergy risk in some individuals.

Works Well With: Standard skincare actives

Avoid Combining With: No known significant incompatibilities

SCIENTIFIC NOTE

Avobenzone's photodegradation discovery drove development of photostabilisation technology — the period from avobenzone's 1978 introduction to development of effective photostabilisers in the 1990s was marked by sunscreens with inadequate uva durability. bemotrizinol (tinosorb s) development provided the most elegant solution by providing a photostable molecule with equivalent uva coverage.

Last Verified: Cosing database,fda uv filter otc monograph,shaath sunscreen photostabilisation review

Primary Sources: 2026-03-12

DESCRIPTION

What It Does: Provides specialty silicone performance — elastomeric skin feel, water-soluble silicone activity, or enhanced hair cuticle conditioning — depending on the specific functional modification.

Why It's Used: Specialty silicones deliver performance profiles unavailable from standard dimethicone: amine-modified (amodimethicone) provides the strongest hair cuticle substantivity; crosslinked elastomers provide the unique velvet-bounce feel; peg-grafted forms provide water compatibility.

How It Works: Functional modification determines mechanism: amine groups (amodimethicone) electro-statically bind negatively charged hair cuticle providing substantive conditioning deposition; crosslinks create elastic network providing deformation-recovery (velvet feel); peg grafts increase hlb providing water miscibility.

Typically Found In: Hair conditioners,primers,specialty formulas

TECHNICAL DETAILS

Primary Category: Functional ingredient – emollient

Secondary Functions: Barrier sealing,softening

Application Areas:

Facial Skincare

Body Care

Hair Care

Beard Care

Color Cosmetics (Makeup)

Dietary/Oral Supplements

Typical Concentration Range: 0.5%–20%

SOURCING & ETHICS

Vegan Status: Yes

Halal Status: Yes

Source Notes: Plant-derived, synthetic or animal-derived. verify source.

SKIN COMPATIBILITY

Irritancy Rating: 1/5 – very low

Comedogenicity Rating: 1/5 – low; formulation-dependent

Sensitivity Concerns: Non-irritating.

Safe for Sensitive Skin: Yes

SAFETY & COMPATIBILITY

Safety Profile: Excellent safety profile. ewg score: 1.

Works Well With: Humectants,ceramides,actives as carrier

Avoid Combining With: No significant incompatibilities

SCIENTIFIC NOTE

Amodimethicone's amine groups have pka ~9 — at typical conditioner ph 4–5, they are fully protonated (–nh₃⁺) providing maximum cationic character for electrostatic attraction to negatively charged damaged hair cuticle.

Last Verified: Cosing database,specialty silicone performance review

Primary Sources: 2026-03-12

DESCRIPTION

What It Does: Glycerin pulls water from the environment and deeper skin layers into the outer skin layer (epidermis), boosting moisture levels and keeping skin soft, smooth, and plump.

Why It's Used: It is used in virtually every moisturizer, serum, and cleanser because it is highly effective at hydrating skin, is well-tolerated by all skin types, and enhances the texture and spreadability of formulations.

How It Works: As a humectant, glycerin forms hydrogen bonds with water molecules, trapping them in the skin. it also reinforces the skin barrier by integrating into lipid structures between skin cells.

Typically Found In: Moisturizers,serums,cleansers,toners,sheet masks,sunscreens,body lotions,shampoos,conditioners

TECHNICAL DETAILS

Primary Category: Humectant

Secondary Functions: Skin barrier support,emollient,solvent

Application Areas:

Facial Skincare

Body Care

Hair Care

Beard Care

Color Cosmetics (Makeup)

Dietary/Oral Supplements

Typical Concentration Range: 1%–30% (typical: 3–10%)

SOURCING & ETHICS

Vegan Status: Yes – plant-derived (coconut, soy, palm) or synthetic

Halal Status: Yes – when plant-derived or synthetic; verify source with supplier

Source Notes: Derived from plant oils via hydrolysis or saponification; synthetic versions also available. palm-derived glycerin carries sustainability concerns.

SKIN COMPATIBILITY

Irritancy Rating: 1/5 – very low; non-irritating at all standard concentrations

Comedogenicity Rating: 0/5 – non-comedogenic

Sensitivity Concerns: Extremely rare allergic reactions; generally safe for all skin types including sensitive and baby skin

Safe for Sensitive Skin: Yes

SAFETY & COMPATIBILITY

Safety Profile: Widely recognized as safe. ewg hazard score: 1. no significant concerns for irritation, sensitization, or toxicity at typical concentrations (up to 50%).

Works Well With: Hyaluronic acid,ceramides,niacinamide,panthenol,urea,peptides,retinol,ahas/bhas

Avoid Combining With: No known incompatibilities at standard concentrations

SCIENTIFIC NOTE

Glycerin is an endogenous skin component found naturally in the stratum corneum. aquaporin-3 channels in keratinocytes facilitate glycerin transport, making it integral to natural skin hydration pathways.

Last Verified: Cosing database,cir safety assessment,ewg skin deep,inci decoder

Primary Sources: 2026-03-12

DESCRIPTION

What It Does: Provides uvb filtration and co-solvent function enabling higher uv filter concentrations in high-spf formulas.

Why It's Used: Spf enabler — homosalate's co-solvent function dissolves other uv filters more completely, enabling higher concentrations and therefore higher achievable spf in fluid-texture formulations.

How It Works: Cyclohexyl salicylate absorbs uvb (λmax 306nm, εmax 4,290 — moderate). also acts as oily co-solvent dissolving avobenzone, octinoxate, and other uv filters. photostable cyclohexyl structure.

Typically Found In: High-spf combination sunscreens

TECHNICAL DETAILS

Primary Category: Active ingredient – cyclohexyl salicylate uvb filter

Secondary Functions: Skin conditioning

Application Areas:

Facial Skincare

Body Care

Hair Care

Beard Care

Color Cosmetics (Makeup)

Dietary/Oral Supplements

Typical Concentration Range: Up to 15% (eu), 10% (us fda)

SOURCING & ETHICS

Vegan Status: Yes – synthetic

Halal Status: Yes

Source Notes: Commercially produced for cosmetic use. verify vegan/halal status with supplier.

SKIN COMPATIBILITY

Irritancy Rating: 1/5 – very low

Comedogenicity Rating: 0/5 – non-comedogenic

Sensitivity Concerns: Well-tolerated by most skin types.

Safe for Sensitive Skin: Yes

SAFETY & COMPATIBILITY

Safety Profile: Eu max 15% (sccs 2019 reduced limit). fda: 10%. potential endocrine activity at high concentrations. ewg score: 4.

Works Well With: Standard skincare actives

Avoid Combining With: No known significant incompatibilities

SCIENTIFIC NOTE

Homosalate's maximum concentration in eu was reduced from 10% to 15% in sccs opinion 2019 (counter-intuitively raised, not reduced) specifically to enable effective uv filter dissolution — demonstrating that homosalate's primary value is as a co-solvent enabling other uv filters to function, not solely as a uv filter itself.

Last Verified: Cosing database,fda uv filter otc monograph,sccs homosalate opinion

Primary Sources: 2026-03-12

DESCRIPTION

What It Does: Creates maximum skin soft-focus effect through refractive-index-matched mie scattering — blurring pores and fine lines while maintaining accurate skin colour reproduction without the whitening caused by high-ri particles.

Why It's Used: Pmma's ri 1.49 precisely matches average skin ri providing optimal scattering efficiency: too-high ri (glass 1.52) over-scatters causing whitening; too-low ri creates high contrast scatter. pmma's ri match provides maximum blur-to-colour-shift ratio.

How It Works: Suspension polymerisation produces perfectly spherical pmma particles 5-20 um. mie scattering cross-section peaks when particle diameter is approximately the wavelength of light. pmma (ri 1.49) vs skin (ri ~1.46) provides small ri contrast generating forward-dominant diffuse scatter that softens specular skin reflections without strong whitening.

Typically Found In: Face powders,foundation,primers

TECHNICAL DETAILS

Primary Category: Active ingredient – cosmetic active

Secondary Functions: Skin conditioning

Application Areas:

Facial Skincare

Body Care

Hair Care

Beard Care

Color Cosmetics (Makeup)

Dietary/Oral Supplements

Typical Concentration Range: 1%–20%

SOURCING & ETHICS

Vegan Status: Yes

Halal Status: Yes

Source Notes: Commercially produced for cosmetic use. verify vegan/halal status with supplier.

SKIN COMPATIBILITY

Irritancy Rating: 1/5 – very low

Comedogenicity Rating: 0/5 – non-comedogenic

Sensitivity Concerns: Well-tolerated by most skin types.

Safe for Sensitive Skin: Yes

SAFETY & COMPATIBILITY

Safety Profile: Good safety profile at recommended concentrations. ewg score: 1–2.

Works Well With: Standard skincare actives

Avoid Combining With: No known significant incompatibilities

SCIENTIFIC NOTE

Eu microplastic regulatory note: insoluble spherical pmma particles in rinse-off products may fall within 2023/2055 restriction scope. leave-on make-up is likely exempt but rinse-off use requires compliance verification by particle size and solubility criteria.

Last Verified: Cosing database,eu regulation 2023/2055,pmma soft-focus optical review

Primary Sources: 2026-03-12

DESCRIPTION

What It Does: Absorbs uva (320–400 nm) and/or uvb (290–320 nm) photons with a high molar extinction coefficient, dissipates absorbed energy as vibrational heat, and contributes to the formulation's spf and critical wavelength.

Why It's Used: Organic uv filters are selected for their high molar extinction coefficient (>10,000 l/mol/cm for most commercial filters), specific spectral coverage complementing other filters in the system, and photostability under prolonged uv exposure.

How It Works: Aromatic π→π* and n→π* electronic transitions absorb uv photons exciting the chromophore to a singlet excited state (s₁). ultra-fast internal conversion (10⁻¹²–10⁻¹¹ s) dissipates excitation energy as heat rather than photochemical reactions, returning the molecule to the ground state for continued absorption.

Typically Found In: Sunscreens,spf formulas

TECHNICAL DETAILS

Primary Category: Active ingredient – cosmetic active

Secondary Functions: Skin conditioning

Application Areas:

Facial Skincare

Body Care

Hair Care

Beard Care

Color Cosmetics (Makeup)

Dietary/Oral Supplements

Typical Concentration Range: Check local sunscreen limits

SOURCING & ETHICS

Vegan Status: Yes

Halal Status: Yes

Source Notes: Commercially produced for cosmetic use. verify vegan/halal status with supplier.

SKIN COMPATIBILITY

Irritancy Rating: 1/5 – very low

Comedogenicity Rating: 0/5 – non-comedogenic

Sensitivity Concerns: Well-tolerated by most skin types.

Safe for Sensitive Skin: Yes

SAFETY & COMPATIBILITY

Safety Profile: Good safety profile at recommended concentrations. ewg score: 1–2.

Works Well With: Standard skincare actives

Avoid Combining With: No known significant incompatibilities

SCIENTIFIC NOTE

Organic uv filter photostability varies significantly — avobenzone degrades rapidly alone but is stabilised by octocrylene (energy quenching) or triazine-class filters (direct stabilisation). filter combination selection must account for photostabilisation requirements of each component.

Last Verified: Cosing database,organic uv filter photostability combination review

Primary Sources: 2026-03-12

DESCRIPTION

What It Does: Provides uvb-uva-ii uv protection and essential avobenzone photostabilisation.

Why It's Used: The essential combination partner — octocrylene's dual uv filter + avobenzone photostabilisation function makes it virtually irreplaceable for durable broad-spectrum chemical sunscreens requiring uva-i coverage.

How It Works: Cyanocinnamate chromophore absorbs uvb-uva-ii (λmax 303nm). triplet energy transfer from excited avobenzone to octocrylene photostabilises avobenzone (>90% efficiency at 3:1 avobenzone:octocrylene ratio). hydrophobic character enhances water resistance.

Typically Found In: Broad-spectrum sunscreens,avobenzone-containing formulas

TECHNICAL DETAILS

Primary Category: Active ingredient – uv filter and photostabiliser

Secondary Functions: Skin conditioning

Application Areas:

Facial Skincare

Body Care

Hair Care

Beard Care

Color Cosmetics (Makeup)

Dietary/Oral Supplements

Typical Concentration Range: Up to 10% (eu), 10% (us fda)

SOURCING & ETHICS

Vegan Status: Yes – synthetic

Halal Status: Yes

Source Notes: Commercially produced for cosmetic use. verify vegan/halal status with supplier.

SKIN COMPATIBILITY

Irritancy Rating: 1/5 – very low

Comedogenicity Rating: 0/5 – non-comedogenic

Sensitivity Concerns: Well-tolerated by most skin types.

Safe for Sensitive Skin: Yes

SAFETY & COMPATIBILITY

Safety Profile: Eu max 10%. fda: 10%. ewg score: 3. recent benzophenone impurity concerns from aged product hydrolysis under study.

Works Well With: Standard skincare actives

Avoid Combining With: No known significant incompatibilities

SCIENTIFIC NOTE

Octocrylene's triplet energy transfer photostabilisation of avobenzone operates via a dexter electron exchange mechanism: excited-state avobenzone (triplet) transfers excitation energy to octocrylene via orbital overlap, allowing avobenzone to return to its ground state uv-absorbing form without photodegradation. this energy transfer is only efficient at close molecular proximity — requiring intimate mixing of the two compounds in the formulation oil phase.

Last Verified: Cosing database,fda uv filter otc monograph,sccs octocrylene opinion

Primary Sources: 2026-03-12

DESCRIPTION

What It Does: Provides humectant moisture retention with antimicrobial preservative-boosting activity.

Why It's Used: The balanced multifunctional diol — pentylene glycol provides the ideal balance of humectancy and antimicrobial activity for clean beauty preservation systems with excellent sensory compatibility.

How It Works: C5 diol: longer chain than propylene glycol providing better antimicrobial activity but shorter than 1,2-hexanediol (slightly lower membrane activity). two oh groups provide humectant water binding. solvent for fragrances and some actives. synergistic with phenoxyethanol reducing required phenoxyethanol concentration.

Typically Found In: Clean beauty products,natural preservation systems,moisturisers

TECHNICAL DETAILS

Primary Category: Functional ingredient – multifunctional pentanediol

Secondary Functions: Tewl reduction,skin plumping

Application Areas:

Facial Skincare

Body Care

Hair Care

Beard Care

Color Cosmetics (Makeup)

Dietary/Oral Supplements

Typical Concentration Range: 0.5%–3%

SOURCING & ETHICS

Vegan Status: Yes – synthetic

Halal Status: Yes

Source Notes: Synthetic or naturally derived. excellent aqueous solubility.

SKIN COMPATIBILITY

Irritancy Rating: 1/5 – very low

Comedogenicity Rating: 0/5 – non-comedogenic

Sensitivity Concerns: Non-irritating; suitable for all skin types.

Safe for Sensitive Skin: Yes

SAFETY & COMPATIBILITY

Safety Profile: Excellent safety profile. ewg score: 1.

Works Well With: Ceramides,emollients,occlusives,glycerin,hyaluronic acid

Avoid Combining With: No significant incompatibilities

SCIENTIFIC NOTE

Pentylene glycol's position in clean beauty preservation is due to a regulatory quirk: 1,2-pentanediol is not classified as a preservative in eu cosmetics regulations (unlike phenoxyethanol which requires preservative listing), so it can provide antimicrobial activity while not requiring the 'contains preservative' designation — enabling cleaner labels in natural-positioned formulations.

Last Verified: Cosing database,dsm hydrolite-5 technical data,cir safety assessment

Primary Sources: 2026-03-12

DESCRIPTION

What It Does: Prevents microbial contamination and spoilage in cosmetic formulations.

Why It's Used: The benchmark cosmetic preservative – eu-permitted up to 1%, effective against virtually all cosmetically relevant microorganisms, and excellent tolerability.

How It Works: Phenol ring provides broad antimicrobial activity via disruption of bacterial and fungal cell membranes and inhibition of enzymatic activity. effective against gram-positive and gram-negative bacteria, yeasts (candida), and molds (aspergillus). activity ph range: 3-9.

Typically Found In: All cosmetic formulations as primary preservative

TECHNICAL DETAILS

Primary Category: Functional ingredient – broad-spectrum preservative

Secondary Functions: Skin conditioning

Application Areas:

Facial Skincare

Body Care

Hair Care

Beard Care

Color Cosmetics (Makeup)

Dietary/Oral Supplements

Typical Concentration Range: 0.1%–1% (eu max 1%)

SOURCING & ETHICS

Vegan Status: Yes – synthetic

Halal Status: Yes

Source Notes: Commercially produced for cosmetic use. verify vegan/halal status with supplier.

SKIN COMPATIBILITY

Irritancy Rating: 1/5 – very low

Comedogenicity Rating: 0/5 – non-comedogenic

Sensitivity Concerns: Well-tolerated by most skin types.

Safe for Sensitive Skin: Yes

SAFETY & COMPATIBILITY

Safety Profile: Eu cosmetics regulation max 1%. sccs assessed as safe at ≤1%. avoid use around eyes in baby products per some country regulations. ewg score: 4.

Works Well With: Standard skincare actives

Avoid Combining With: No known significant incompatibilities

SCIENTIFIC NOTE

Phenoxyethanol's widespread adoption as the primary cosmetic preservative followed the phaseout of parabens from many formulations in the 2000s-2010s. despite having a comparable or better safety profile to parabens, it is often cited in 'free-from' formulations – a consumer perception issue rather than a scientific safety concern.

Last Verified: Cosing database,sccs opinion on phenoxyethanol,cir safety assessment

Primary Sources: 2026-03-12

DESCRIPTION

What It Does: Provides antioxidant protection, soothing anti-inflammatory effects, and skin-conditioning benefits through plant-derived polyphenols and phytochemicals.

Why It's Used: Plant extracts concentrate bioactive phytochemicals evolved for environmental protection — uv, microbial, and oxidative stressors — that translate to skin benefits.

How It Works: Polyphenols (flavonoids, phenolic acids) inhibit nf-κb-mediated inflammatory signaling, scavenge reactive oxygen species through electron donation, and chelate pro-oxidant metal ions to reduce oxidative skin damage.

Typically Found In: Lotions,creams,serums,masks

TECHNICAL DETAILS

Primary Category: Minerals

Secondary Functions: Skin-conditioning

Application Areas:

Facial Skincare

Body Care

Hair Care

Beard Care

Color Cosmetics (Makeup)

Dietary/Oral Supplements

Typical Concentration Range: 0.1–10%

SOURCING & ETHICS

Vegan Status: Yes

Halal Status: Yes

Source Notes: Mineral-derived ingredient; no biological origin.

SKIN COMPATIBILITY

Irritancy Rating: 1

Comedogenicity Rating: 0

Sensitivity Concerns: Low sensitization potential at recommended use concentrations.

Safe for Sensitive Skin: Yes

SAFETY & COMPATIBILITY

Safety Profile: Well-characterized cosmetic ingredient with established safety profile. generally non-irritating at typical use concentrations. suitable for leave-on and rinse-off cosmetics.

Works Well With: Plant extracts,peptides,vitamins

Avoid Combining With: Strong chelating agents (reduce mineral availability)

SCIENTIFIC NOTE

Plant secondary metabolites (flavonoids, terpenes, phenolic acids) are biosynthesized as defense compounds against uv, herbivores, and pathogens. their anti-inflammatory activity typically derives from competitive inhibition of cox-2 and 5-lox enzymes (ic50 1–50 µm), while antioxidant activity involves single electron transfer (set) and hydrogen atom transfer (hat) mechanisms with structure-dependent rate constants.

Last Verified: Cosing eu database; pcpc cosmetic ingredient safety reviews; ingredient-specific safety and efficacy literature

Primary Sources: 2025-01-15