Why the Dye?

The many colors of FEES

You’ve maybe witnessed a FEES exam.   It can sometimes be quite colorful.

Often, green food coloring is used during the exam.   This helps to make the bolus “stand out” in the pharynx.   You may also see blue food coloring used or even white food coloring or naturally white foods such as milk to really make the materials visible if aspirated.

Silent aspiration

Silent aspiration has been reported in over 40% of patients referred for evaluation of swallowing in a rehabilitation hospital and as many as 77% of ventilator-dependent patients have silent aspiration.   It is imperative that we are able to “see” the aspiration.

Study using blue food coloring

In a study by Leder, Acton, Lisitano and Murray (2005), 20 adults were evaluated using FEES, 9 subjects with food that was dyed blue (2 drops of blue in 60cc of pudding and 120 cc of milk) and 11 subjects with regular non-dyed food (yellow pudding, white skim milk).

The study looked at 4 areas:

  1.  the stage transition characterized by depth of bolus flow to at least the vallecula prior to the pharyngeal swallow.
  2. evidence of bolus retention in the vallecula or pyriform sinuses after the pharyngeal swallow
  3. laryngeal penetration
  4. tracheal aspiration

Three SLPs interpreted the studies with 100% agreement in the non-dyed food and in the dyed food.

The dye was changed to green from blue after several deaths resulted from blue dye that was placed in tube feeding.

This study found that the “important variable in detecting both bolus flow to and location in the pharynx and larynx is how well a bolus reflects light (it must be brighter than the tissue it is resting on).   Therefore, the endoscopist can be assured of reliable FEES results using regular, non-dyed food trials.”

Study using green food coloring

Another study by Marvin, Gustafson and Thibeault found that the use of green food coloring improved judgement of airway invasion as compared to white foods.    


Leder, S. B., Acton, L. M., Lisitano, H. L., & Murray, J. T. (2005). Fiberoptic endoscopic evaluation of swallowing (FEES) with and without blue-dyed food. Dysphagia20(2), 157-162.

Marvin, S., Gustafson, S., & Thibeault, S. (2016). Detecting aspiration and penetration using FEES with and without food dye. Dysphagia31(4), 498-504.

Splaingard, M. L., Hutchins, B., Sulton, L. D., & Chaudhuri, G. (1988). Aspiration in rehabilitation patients: videofluoroscopy vs bedside clinical assessment. Archives of physical medicine and rehabilitation69(8), 637-640.

Elpern, E. H., Scott, M. G., Petro, L., & Ries, M. H. (1994). Pulmonary aspiration in mechanically ventilated patients with tracheostomies. Chest105(2), 563-566.

One thought on “Why the Dye?

  1. Thanks for the information! I’ve done MBSS for 14 years so I’m learning as much as I can about FEES. I’m not trained in FEES but hope to be soon. This information is helpful.

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