Determination
David Woolley, Adam Woolley in Practical Toxicology, 2017
Before looking at the testing needed to evaluate these three endpoints, it is worth considering their characteristics: Irritation is a reversible nonimmunological response at the site of contact, which may be seen as erythema (reddening of the skin) or edema (thickening due to accumulation of fluid under the skin).Corrosion is not reversible and is characterized by the production of irreversible damage at the site of contact as a result of chemical reaction. Both irritation and corrosion are dose-dependent reactions.Sensitization is an immunological reaction that, while it has dose dependency in the induction stage, is not clearly dose dependent following induction. Furthermore, the amounts of chemical needed to elicit an allergic reaction are much smaller than those needed during the induction phase.
Skin Morphology, Development and Physiology
Heather A.E. Benson, Michael S. Roberts, Vânia Rodrigues Leite-Silva, Kenneth A. Walters in Cosmetic Formulation, 2019
Perturbation of barrier function sometimes, but not always, also induces an inflammatory response that results in irritation. It is important to appreciate that ‘irritation’ is used to describe skin reactions that can range from a mild and transient erythema and/or itch to serious vesiculation. The application of the surfactant sodium dodecyl sulphate (SDS) almost always results in an irritant response (Patil et al., 1994; Angelova-Fischer et al., 2016). SDS intercalates with the lamellae and increases fluidity in this region resulting in an increase in TEWL. Furthermore, although other surface-active agents, such as sodium laurate and polysorbates, can increase TEWL to similar levels as SDS, the resultant irritation is much less and in some cases, not significantly different to untreated skin. It follows that irritation subsequent to exposure to SDS must be a result of factors other than an increase in water transport and the stimulation of lipogenesis.
Evaluating Performance Benefits of Conditioning Formulations on Human Skin
Randy Schueller, Perry Romanowski in Conditioning Agents for Hair and Skin, 2020
At baseline, subjects begin using the treatment product assigned, usually twice per day for up to 6 months. Clinical assessment of the effectiveness and irritation of the treatment is usually conducted at monthly intervals. Assessment of irritation includes erythema (skin redness), edema (skin swelling), scaling (skin dryness), acne breakouts, and the subjective sensations of burning, stinging, itching, tightness, and tingling. Bioinstrumentation methods are often employed to substantiate clinical improvement. These include silicone replicas with image analysis for fine lines and wrinkles, D-Squame Disk sampling of surface skin cells (squame) to assess desquamation pattern, conductance meter measurements (e.g., NOVA Dermal Phase Meter or SKICON Skin Surface Hygrometer) to evaluate skin hydration, skin elasticity measurements (e.g., Cutometer SEM 474 or Ballistometer, Hargens), and colorimeter measurements (e.g., Minolta Tri-Stimulus Colorimeter) to evaluate skin clarity changes. In addition, high-quality clinical documentation photography is sometimes employed to document clinical improvement (see Section II.C.2).
Exploring the potential of minoxidil tretinoin liposomal based hydrogel for topical delivery in the treatment of androgenic alopecia
Published in Cutaneous and Ocular Toxicology, 2020
Pratiksha Kochar, Kritika Nayak, Shreya Thakkar, Suryanarayan Polaka, Dignesh Khunt, Manju Misra
As shown in Figure 6(C), there was no sign of irritation observed in any of the animals which suggested that the developed liposomes along with hydrogel loaded with those liposomes are non-irritant and exhibit no/lesser toxicity. Skin irritation is complex biological sequence involving variety of cytokines which usually manifest as erythema, redness or itching etc61. There are several in vitro and in vivo tests or protocols available today but among them, Draize’s test has been widely accepted and approved test for skin irritation62. When developed formulations were applied on rat skin, they did not show any irritation similar to one applied with marketed formulations. Plain drug solution, individual drug loaded liposomes and liposomes loaded with combination of drugs; none showed any visual sign of irritation. TRET is well known for its irritancy potential. Still no significant irritation was observed even in hydrogel loaded with MXD and TRET. It must be attributed by hydrogel; the dosage form. As all were applied as hydrogel, it could be inferred that the dosage form itself had protecting impact on site of application63.
Potential role of resveratrol-loaded elastic sorbitan monostearate nanovesicles for the prevention of UV-induced skin damage
Published in Journal of Liposome Research, 2020
Skin irritation. The irritancy of the selected drug-loaded nanovesicles and drug suspension was evaluated according to the Draize method with some modifications (Draize et al.1944, Kamel and Abbas 2013). The dorsal side of the rat was shaved 24 h before the beginning of the experiment. The animals were divided into 4 groups each containing 6 rat: group 1 served as control (no treatment), group 2 received 0.8% v/v aqueous formalin solution as a standard irritant (Bharkatiya et al.2010), while group 3 and 4 received the selected drug-loaded nanovesicles and drug suspension, respectively. An amount of 1 ml of the tested formula (or formalin solution) was applied once daily for 72 h. The application sites were visually examined for oedema and erythema at 24 and 72 h and graded from 0–4 according to standard score. Score 0 indicates no erythema or oedema, while score 4 indicated the highest degree. The final score represents the average of the 24 and 72 h readings. The primary irritancy index (PII) was determined for each preparation by adding the oedema and erythema scores, the formulations were accordingly classified as nonirritant if PII <2, irritant if PII = 2–5 and highly irritant if PII = 5–8.
Topical phenytoin nanostructured lipid carriers: design and development
Published in Drug Development and Industrial Pharmacy, 2018
Amira Motawea, Thanaa Borg, Abd El-Gawad H. Abd El-Gawad
Phenytoin was clinically used for management of epilepsy and cardiac arrhythmia. Gingival hyperplasia has been declared to occur as a side effect in as many as 50% of patients with epilepsy receiving long-term oral phenytoin therapy [1]. This apparent stimulatory effect on the growth of connective tissue submits its topical use as a wound healing agent [2]. Numerous studies have been conducted on phenytoin to promote the healing of decubitus ulcers [3], epidermolysis bullosa [4], recalcitrant neuropathic diabetic foot ulcers [2], venous stasis ulcers [5], traumatic wounds, burns, and leprosy trophic ulcers [6]. Phenytoin is commercially available as a topical spray with high content of organic solvents (such as 70% ethyl alcohol and/or propylene glycol). Unfortunately, its use is limited for once-daily administration to avoid the severe side effects accompanied with its high percentage of organic solvents. Examples of the side effects identified are skin dryness, burning, irritation, redness, and allergic contact dermatitis. Thus, there is a crucial need for new organic solvent-free topical formulations that can promote phenytoin wound healing ability with minimal or no adverse effects [7].