Chaparral (Larrea tridentata), or creosote bush, is one of the most widely utilized plants in Indigenous Southwestern medicine. Tribes including the Cahuilla, Pima, and Apache have long applied poultices of its leaves and stems to treat skin infections, wounds, fungal eruptions, and rheumatic pain.^4,8 Preparations such as “chaparral tea” or resinous compresses were also used ceremonially and for purifying the skin after environmental exposure.

The primary bioactive compound in L. tridentata is nordihydroguaiaretic acid (NDGA), a potent lignan that can comprise up to 50% of the leaf resin.⁷ Other constituents include quercetin, catechins, flavonolignans, saponins, and essential oils. NDGA and its derivatives possess powerful antioxidant, anti-inflammatory, and antimicrobial properties, making them pharmacologically promising yet controversial due to toxicity concerns (Table 2).^7,8

325537 Table 2.

NDGA exhibits dual lipoxygenase and cyclooxygenase inhibition, reducing leukotrienes and prostaglandins central to cutaneous inflammation. In vitro assays show superoxide scavenging capacity surpassing vitamin C, and significant reductions in TNF-α, IL-1β, and COX-2 activity.^7,9 NDGA also activates the NRF2 antioxidant pathway while simultaneously downregulating redox-sensitive inflammatory genes like Sp1 and NF-κB.⁹ Recent hydrogel-based formulations using Larrea extract enhanced fibroblast adhesion and promoted wound healing in vivo without cytotoxicity.¹⁰

Modern studies affirm the plant’s broad-spectrum antimicrobial activity, with ethanol extracts showing >99.9% inhibition against Staphylococcus aureus, Pseudomonas aeruginosa, and Malassezia spp.¹¹ The mechanisms likely involve phenolic disruption of microbial membranes and fungal β-1,3-glucanase inhibition.⁴

Although L. tridentata is non-cytotoxic in vitro at topical concentrations, its use is limited by the systemic hepatotoxicity of NDGA. High-dose ingestion has been associated with nephropathy and bile duct injury, leading to its removal from the Food and Drug Administration (FDA) food additive lists.^8,9 However, as of late, newer methylated derivatives (eg, M4N) and nanocarrier formulations are being developed to retain bioactivity while mitigating systemic toxicity.¹² For dermatologic use, topical application of controlled-extract preparations remains the safest and most effective route.

L. tridentata exemplifies the intersection of ancestral Indigenous knowledge and modern phytomedicine. Its NDGA-rich profile offers compelling anti-inflammatory, antioxidant, and antimicrobial potential for skin conditions such as eczema, infected wounds, and fungal dermatoses. While internal use carries toxicity risk, topical formulations rooted in traditional poultice methods offer a culturally grounded and scientifically supported therapeutic avenue.

Yucca, known as the “soap root” or “desert cleanser,” holds deep ethnobotanical significance for Indigenous communities across the Southwest, including the Navajo, Apache, and Pueblo peoples. Traditionally, yucca roots were pulverized to create foamy skin washes used to cleanse wounds, soothe eczema, and reduce joint swelling.^1,13 Yucca was also ritually used to purify the scalp, promote hair growth, and relieve inflammation of the skin, scalp, and joints, particularly through intergenerational ceremonial practice among the Yoeme and Hopi.¹⁴

Yucca is pharmacologically rich in steroidal saponins, which confer both its foaming and medicinal properties. Studies have identified over 100 saponins from various Yucca species, with prominent spirostanic structures such as yuccaloeside A–E and gloriosaol A–E, as well as flavonoids like quercetin, luteolin, apigenin, and resveratrol.^15–17 Other key constituents include phenolic acids (caffeic acid, gallic acid), shikimic acid, and anti-inflammatory stilbenes such as trans-4,4′-dihydroxystilbene.¹⁸ (Table 3).

325538 Table 3.

Yucca’s anti-inflammatory activity is driven by the suppression of multiple cytokines and signaling pathways. Yucca root and leaf extracts downregulate TNF-α, IL-1β, IL-6, and COX-2 expression, while also inhibiting the NF-κB, JAK/STAT, and MAPK (p38, ERK1/2, JNK) pathways.^16,17 The saponins and stilbenes act in synergy to inhibit nitric oxide production via iNOS and reduce reactive oxygen species through Nrf2 activation.¹³ Notably, yuccaol A and C have been shown to inhibit β-glucuronidase and NO in macrophages, suggesting a role in chronic inflammatory dermatoses. In a carrageenan-induced rat paw model, Yucca gigantea extract significantly lowered TNF-α and COX-2, improved histologic skin structure, and restored GSH levels.¹⁶

Yucca’s saponin-rich butanolic extracts inhibit both Gram-positive (Staphylococcus aureus) and Gram-negative (E. coli, P. aeruginosa) bacterial growth, as well as Candida albicans and other fungi.¹³ The amphipathic nature of saponins allows membrane disruption and antimicrobial penetration, while the plant’s high antioxidant capacity, measured via DPPH, ORAC, and FRAP assays, supports its ability to mitigate oxidative barrier damage.¹⁷

Yucca’s traditional cleansing function translates well into modern dermatology as a gentle topical adjunct for inflammatory conditions like eczema, especially when compounded into soaps, hydrosols, or foaming gels. Clinical formulations that harness its saponins and flavonoids show promise in restoring the skin barrier, scavenging free radicals, and reducing microbial colonization, all without the steroid-associated side effects. As a bonus, topical preparations avoid the hepatotoxicity observed in oral saponin overdoses and maintain favorable safety profiles in vivo.^8,15

Yucca exemplifies a desert-adapted botanical whose intergenerational use for skin inflammation has been mechanistically validated by contemporary science. Its rich content of steroidal saponins, anti-inflammatory flavonoids, and barrier-protective antioxidants supports its continued exploration in integrative dermatology, especially for conditions like eczema, contact dermatitis, and infected wounds. With minimal toxicity and deep cultural roots, Yucca spp. stand as a symbol of the harmony between Indigenous plant wisdom and biomedical innovation.

Known to many Indigenous Southwestern tribes as a sacred purifying agent, Juniperus monosperma (commonly referred to as desert cedar) has long been used in ceremonial steam baths, smoke cleansing rituals, and topical poultices. Among the Diné (Navajo), Pueblo, and Apache peoples, crushed needles and berries were applied to swollen joints and inflamed skin, while aromatic steam infusions were used to treat respiratory conditions and cleanse the spirit.^1,14 Juniper smoke, in particular, played a dual medicinal and spiritual role, believed to detoxify both the skin and the mind.

The resin-rich needles and berries of J. monosperma are high in monoterpenes such as α-pinene, sabinene, limonene, and particularly α-thujone, an oxygenated monoterpenoid also present in Eastern white cedar (Thuja occidentalis).^19,20 Other constituents include β-thujone, camphene, and terpineol derivatives, all contributing to its distinctive aroma and potent biological activity. These volatile oils act as both antimicrobial agents and skin stimulants.

Essential oils from various Juniperus species, including J. monosperma analogs such as J. communis and J. chinensis, exhibit robust antimicrobial and anti-inflammatory activity. In vitro studies show that α-pinene and β-thujone inhibit the production of pro-inflammatory cytokines like TNF-α, IL-1β, and IFN-γ via suppression of NF-κB and iNOS pathways.¹⁹ Lipid peroxidation markers such as MDA are also reduced, indicating antioxidant capacity. Antimicrobial assays reveal that J. communis oil possesses MIC values as low as 4.75 µg/mL against S. aureus, with comparable activity against E. coli and various fungal strains including Aspergillus and Trichophyton.^19,20 These results, though derived from close relatives, are likely translatable to J. monosperma, given the shared chemical profile and traditional usage overlap.

Cedar essential oils are increasingly incorporated into topical formulations aimed at treating acne, contact dermatitis, and oily skin conditions due to their astringent and purifying properties. In integrative dermatology, hydrosols and diluted essential oil preparations derived from this species are used for wound cleansing, fungal skin infections, and even scalp conditions such as seborrheic dermatitis.¹ It’s vasodilatory and circulation-enhancing actions also make it a candidate for post-inflammatory hyperpigmentation care. However, due to thujone’s known neurotoxicity at high doses, formulation safety requires precise dilution, especially for application on compromised skin or in pediatric populations.²¹

Thujone is a known neurotoxin at high concentrations and may provoke seizures through GABA receptor antagonism. Regulatory agencies, including the European Medicines Agency, limit thujone content in topical formulations to prevent systemic absorption.²² Contact dermatitis has also been reported with undiluted or oxidized oils. Therefore, clinical use of J. monosperma must rely on low-dose, well-characterized extracts with known chemotypes. Topical application of diluted cedar oil in carrier bases (eg, jojoba, glycerin) is generally well tolerated when used intermittently.

Cedar, specifically Juniperus monosperma, embodies the integrative potential of plant-based medicine rooted in ceremony, tradition, and science. Its volatile oils, rich in thujone and α-pinene, provide antimicrobial and anti-inflammatory effects validated by modern pharmacology. When formulated responsibly, cedar offers a culturally resonant botanical for treating inflammatory and infectious skin conditions, especially in underserved communities where traditional plant knowledge remains an untapped resource for sustainable dermatologic care.

While not endemic to the American Southwest, Aloe vera has been embraced by Indigenous desert-dwelling communities such as the Yoeme and Xicana peoples as a “hero plant” for treating sunburns, insect bites, and dry, inflamed skin.¹ Traditionally, the fresh inner gel was applied directly to burns and wounds, hydrating and cooling the skin while simultaneously aiding healing. These practices reflect deep environmental adaptation, with aloe serving both medicinal and survival purposes in arid climates.

Aloe vera gel contains over 200 bioactive constituents, including polysaccharides (especially acemannan), glycoproteins, sterols (β-sitosterol), anthraquinones (aloin, aloe-emodin), flavonoids, trace minerals (zinc, magnesium), and salicylic acid.^23,24 Acemannan, a mannose-rich polysaccharide, is considered the principal compound responsible for aloe’s wound healing and immunomodulatory effects.

Aloe’s healing properties are driven by its capacity to reduce inflammation, enhance fibroblast activity, and stimulate collagen synthesis. Acemannan activates macrophages, increases cytokine signaling (IL-6, IL-8, IL-10), and promotes type I collagen production via Smad and MAPK pathways.^23,25 Anthraquinones like aloin inhibit JAK1–STAT1/3 and ROS production, reducing TNF-α, IL-1β, and IL-6 levels.²⁶ Aloe also restores tight junction proteins (eg, claudin-1, ZO-1) and reduces Th2/Th17-driven inflammation in atopic dermatitis models.²⁷ Extracellular vesicles derived from Aloe gel have recently been shown to shift macrophages from pro-inflammatory (M1) to regulatory (M2) phenotypes, offering a novel mechanism of immune modulation.²⁸

Aloe’s traditional uses have been strongly validated by modern clinical trials. A systematic review of 23 human trials found that Aloe significantly accelerated healing in burns, ulcers, cesarean wounds, cracked nipples, and pressure sores, often outperforming standard treatments like silver sulfadiazine and lanolin.²⁹ One randomized trial reported a 29% faster wound healing time and complete closure by day 15 with Aloe hydrogel.³ Another RCT involving 2,248 psoriasis patients showed that an Aloe-propolis ointment led to complete lesion clearance in 64.4% of participants.³⁰ In vitro studies also demonstrate Aloe’s ability to upregulate aquaporin-3 (AQP3), a key protein in skin hydration, by over 380% when combined with betaine.³¹

Aloe is clinically beneficial in:

Aloe is generally well tolerated in topical applications, especially when derived from the inner leaf gel. Rare adverse effects include mild dryness or irritation in sensitive individuals.⁵ Toxicity concerns related to anthraquinones like aloin and aloe-emodin apply mainly to oral preparations or whole leaf extracts; thus, dermatologic formulations adhere to International Aloe Science Council (IASC) guidelines, limiting aloin to <10 ppm.²⁴ Traditional usage of fresh aloe gel aligns with safe, effective application, though commercial dilution often reduces therapeutic potency.

Aloe vera bridges ancient desert knowledge and contemporary skin science, making it a standout example of ethnobotanical convergence. Its polysaccharide- and anthraquinone-rich composition supports epithelial regeneration, collagen synthesis, cytokine modulation, and hydration, properties corroborated by robust clinical and molecular data. For Indigenous and integrative dermatology alike, Aloe vera remains a culturally meaningful and biologically powerful ally in the treatment of inflammatory skin conditions.