Histology: Protecting laboratory operators’ hands during analysis
Histology, the science dedicated to studying biological tissues, plays a fundamental role in laboratories, whether for biomedical research or medical diagnostics. This discipline relies on the analysis of tissue samples collected from human patients, animals, or plants, requiring various preparation steps that often involve handling potentially hazardous chemicals.
Given these exposures, wearing appropriate single-use gloves is essential to protect operators. In this article, we guide you through a standard staining protocol - haematoxylin-eosin staining - focusing on hand protection at each stage of the process.
Handling histology samples: What are the risks?
Histological analyses require manual intervention on samples as well as the use of aggressive chemical reagents for tissue fixation, staining, and preservation.
The primary risks faced by laboratory operators include:
- Chemical risks: Contact with solvents (formaldehyde, xylene, alcohols), fixatives, and dyes.
- Biological risks: Handling potentially infectious samples or those containing pathogens.
- Mechanical risks: Injuries related to handling microtomes and glass slides.
To mitigate these risks, it is crucial to select protective single-use gloves suited to each stage of the process.
Step 1 - Tissue fixation and embedding: Beware of formaldehyde
Fixation is a crucial step to preserve tissue integrity and solidify samples before embedding them in paraffin and sectioning them into ultra-thin slices. Formaldehyde, in which the samples are immersed, is the most commonly used fixative.
Formaldehyde is a toxic reagent upon skin contact, capable of inducing genetic mutations and causing cancer.
Risks associated with formaldehyde:
- Classified as CMR (Carcinogenic, Mutagenic, Reprotoxic).
- Toxic by skin contact or ingestion, potentially fatal by inhalation.
- Can cause severe skin burns, allergic reactions, and significant irritation.
Selecting a single-use glove suitable for handling this reagent is therefore essential for operator safety:
- Nitrile gloves tested against chemical exposure, with acceptable permeation breakthrough time for formaldehyde. The following example of permeation breakthrough time for ecoSHIELD™ Eco Nitrile PF 250 gloves (0.10 mm thick) and duoSHIELD™ PFT Nitrile 240 gloves (0.08 mm thick) illustrates the importance of single-use glove thickness for improved chemical permeation resistance. The thicker the glove, the better the protection!
- Gloves with the lowest possible AQL to minimise the risk of defective gloves with micro-holes. ecoSHIELD™ Eco Nitrile PF 250 gloves, SHIELDskin™ ORANGE NITRILE™ 260 gloves, and SHIELDskin CHEM™ NEO NITRILE™ 300 gloves, manufactured with twinSHIELD™ technology, all have an AQL of 0.25, meaning the risk of micro-holes is nearly zero, offering the highest level of quality and protection.
- Virus-tested gloves for additional protection.
- Gloves with extended cuffs (at least ≥250 mm) to fully cover wrists when handling formaldehyde baths.
After fixation, samples are dehydrated in successive alcohol baths before being embedded in paraffin to facilitate microtome sectioning. The resulting slices are then placed on histology slides.
Step 2 - Deparaffinisation and rehydration: Exposure to toxic solvents
Before staining, paraffin must be removed from histological sections. To achieve this, slides are passed through successive solvent baths, the most commonly used being xylene.
Xylene is highly compatible with the chemicals used in tissue processing. However, once again, operators face exposure risks due to potential spills during solution preparation (often involving decanting) or when transferring slides between baths.
Health risks of xylene exposure:
- Volatile solvent, irritant, and harmful—potentially fatal if swallowed or inhaled.
- Harmful upon skin contact, with a risk of causing skin irritation.
- Presumed risk of serious organ damage following repeated or prolonged exposure.
To mitigate these risks, it is essential to select high-performance single-use gloves for handling this solvent:
- Multi-layered nitrile gloves for enhanced chemical permeation resistance.
- Extended gloves’ cuffs (≥300 mm) to fully protect forearms when transferring samples.
- Gloves tested against xylene, with sufficient permeation breakthrough time for the task performed.
The SHIELDskin CHEM™ NEO NITRILE™ 300 glove is thicker (0.31 mm palm thickness), longer than standard gloves (300 mm), and manufactured with twinSHIELD™ technology, providing unparalleled protection for a single-use glove.
Once paraffin is removed, samples are progressively rehydrated in decreasing alcohol concentrations down to water, preparing the tissues for stain absorption.
Step 3 - Sample staining: Handling acidic and alcohol-based solutions
Histology slides are then sequentially immersed in haematoxylin and eosin baths to reveal cellular structures.
A common protocol involves incubating slides in haematoxylin for 10 minutes, followed by rinsing in water. Samples are then immersed in eosin for 5 to 7 minutes, followed by another rinse.
After staining, samples undergo a final dehydration step, involving another round of alcohol and xylene baths.
Step 4 - Mounting and sample observation
Once all chemical processes are completed, the slices are mounted under coverslips with an appropriate mounting medium, ensuring long-term preservation of the prepared samples.
The technician can then analyse the samples under a microscope.
As highlighted throughout this article, beyond the biological risks posed by the samples, histology lab operators are also exposed to hazardous chemicals in significant volumes (ranging from several hundred millilitres to several litres).
While many pathology departments are now equipped with automated sample preparation systems, numerous research laboratories continue to perform these operations manually, increasing chemical exposure risks.
Formaldehyde for sample fixation and xylene for deparaffinisation pose significant risks to operators, making the selection of appropriate single-use gloves essential.
Key criteria for choosing the right gloves in histology labs:
- Gloves chemical resistance suited to solvents used (formaldehyde, xylene, alcohols).
- Extended gloves’ cuffs (≥250 mm) for enhanced wrist and forearm protection.
- Lowest possible AQL (ideally 0.25) for superior gloves barrier performance.
- Regular glove changes to prevent contamination.
Need Help Selecting the Right Gloves?
👉 Use our Glove Selection Guide or contact a SHIELD Scientific expert for personalised recommendations.
DISCLAIMER: The information provided in this article is for guidance only and may not reflect the user’s specific application. A risk assessment should always be conducted by the purchaser to determine the suitability of gloves for a particular use case.
Share this interesting information
