Thinking of going xylene-free? Here’s what labs should know.

Histotechs know the dangers and health risks associated with xylene, and interest in greener labs continues to grow. As a result, xylene substitutes are gaining more momentum, but switching isn’t just as simple as switching one solution for the other. Since xylene is used in just about every step of the workflow – processing, dehydration, staining, clearing, and coverslipping - every step must be validated. Here are key considerations to keep in mind before making the transition. 

1. Longer processing and staining times 

Most substitutes require longer processing, dehydrating, clearing, and staining steps. Because substitutes behave differently at each stage, labs should expect to adjust station times and thoroughly validate every change before switching.  

2. Deparaffinization and clearing behave differently during staining 

Unlike xylene, many substitutes do not absorb water, which means contamination is harder to detect – there are no visual cues to alert you. Longer deparaffinization times may be needed to fully remove paraffin, and inconsistent clearing can affect tissue detail. Careful monitoring and protocol adjustments are essential. 

3. Mounting media compatibility  

Not all mounting media work well with xylene substitutes; some may cloud, dry improperly, or separate. Always verify compatibility and validate the entire coverslipping process before committing to a switch. Another option is to clear and coverslip straight from alcohol. Isopropyl is a good option for its strong cleaning properties but needs to be fully validated as well. Acrymount Plus mounting media is a great option that works well with most xylene substitutes and isopropyl alcohol. 

4. Higher maintenance load 

Since many substitutes do not absorb water, reagents become contaminated more quickly. This means higher volume labs often need to fully change deparaffinization and dehydration solutions daily, not just rotate them, to maintain consistent quality. 

Tissue processors may also require specialized, longer cleaning cycles optimized for the specific substitute used. Since many substitutes do not act as rapidly or aggressively as xylene, labs should watch closely for paraffin build-up in processing lines and chambers. Additional cleaning steps may be needed to keep the system functioning properly and ensure tissues are adequately processed.  

5. Higher overall cost 

Even though substitutes are safer alternatives, they typically cost more than xylene. When you factor in longer processing times, more frequent reagent changes, and increased processor maintenance, total operational costs can rise. 

So… is it worth switching? This depends on your lab. Xylene substitutes can work, but they are not drop-in replacements, and they require thoughtful adoption.