On the night of Pesah, we will sit down to commemorate the miracles of the Exodus, including the ten devastating plagues that Gd visited upon the Egyptians for persecuting the Hebrew slaves. Rabbi Eliyahu Munk[1] makes the following comment regarding these supernatural events: “In the miracles recorded in the Torah, the supernatural is often interwoven with the natural and the plagues may be defined as miraculously intensified forms of the diseases and other natural occurrences encountered in Egypt.” In other words, these miracles should be viewed as natural events that were supernaturally magnified for the purpose of wreaking havoc in Egypt.

This perspective is consistent with the fundamental precept taught to us by Rav Eliyahu Dessler [2] regarding the concept of miracles.  Rav Dessler taught that there is no essential difference between the “natural” and the “miraculous.”  We use the term “miracle” to describe events that are unusual in our experience, and “natural” in reference to events that occur routinely.  In truth, however, both kinds of events are the manifestation of Gd’s unlimited power and providence.  The frequency and discernible patterns of natural events make it difficult for us to recognize them as acts of Gd, but they are no less an expression of Gd’s might than the greatest miracles. It is thus readily understandable that the miracles in Egypt would unfold according to natural means, as Rav Munk asserted. The intensification of natural phenomena in order to deliver retribution is no less “miraculous” than any miracle Gd has ever performed.

Accordingly, in order to gain a greater understanding and appreciation of these events, we need to study the scientific background to the natural phenomena through which the plagues unfolded.

This article explores the first two of the ten plagues – blood and frogs – through the lenses of several Torah commentaries and the scientific information relevant to these natural phenomena.

First plague: Blood

“So says Hashem: Through this shall you know that I am Hashem – I shall hereby strike the waters that are in the river with the staff in my hand, and they shall change to blood. The fish in the water shall die and the river shall become foul. Egypt will grow weary of trying to drink water from the river.” (Shemot 7:17-18)

Egypt’s Lifeblood Changes to Blood

The river referred to in these verses is the Nile River, the key to the economic life of Egypt, an arid country of which 95 percent is desert. Waters from the Nile River were diverted to streams to irrigate the soil and also to provide a source of freshwater, both for human consumption and for livestock. The Nile River teemed with various species of fish, which were readily consumed by the Egyptians. Periodically, the Nile River overflowed, thereby fertilizing the surrounding soils. The retreating waters left many fish trapped in the grasses, where they were easily available for capture. This may explain Bene Yisrael’s complaint when traveling through the desert, “We remember the fish that we ate in Egypt free of charge” (Bamidbar 11:5).  The Nile River also provided an important transportation route for both people and merchandise. The river was thus the nation’s lifeblood, and Pharaoh considered himself the master, or god, of the Nile. Appropriately, then, the Nile River was the first target of Gd’s plagues, as it was the source of Egypt’s sustenance and success.

The Haggadah mentions that each of the ten plagues consisted of either four (Rabbi Eliezer) or five (Rabbi Akiva) subcomponents. When analyzing the plague of blood, we may point to several different calamities that it incorporated:the Nile River changed to blood, or to a bloodlike substance;

the fish died, leaving the Egyptians without their food staple;

the Nile River fouled and emitted an offensive odor;

the Egyptians lacked a suitable source of drinking water;

the Egyptians grew weary from trying to find drinkable water, and thus had to either purchase drinkable water from Bene Yisrael (Rashi) or dig for underground water (Ibn Ezra).

Rav Avigdor Miller [3] cites the following passages from the admonitions of Ipuwer, an ancient Egyptian papyrus manuscript, which likely refers to the first plague, and gives us a sense of the people’s panic and despair when the river turned to blood: “The river is blood …. Blood is everywhere…. Men shrink from tasting …. That is our water…. What shall we do? Everything is in ruination…”

Real or Fake Blood?

We find among our Torah commentaries two different interpretations of the term “dam” (blood) in the context of this plague. The more common approach is that the Torah speaks here of actual human blood. Rav Yaakov Culi, for example, in his Me’am Loez, writes that this blood in the Nile River had the same taste, smell, and chemical and physical composition of actual blood. The Malbim notes that the Nile River’s water turned to blood and retained some of the characteristics of human blood, most notably its warm temperature, and caused the fish to die. Rabbenu Yosef Bechor Shor likewise comments that the Nile River turned to actual human blood, adding that the blood coagulated, thus causing the fish to die. (See also Targum Onkelos, Maharal, and Seforno.)

Other sources, however, including Targum Yerushalmi Hashalem and Targum Yonatan, explain that the water of the Nile assumed the color and general appearance of blood, but did not actually transform into blood. In a similar vein, Rabbenu Bahya, cited by Rav Zalman Sorotzkin [4], suggested that water of the Nile River took on the appearance, taste, and smell of blood, but was not actual blood. This is also the approach taken by Rav Naftali Zvi Yehuda Berlin (“Netziv”; see Ha’amek Davar, Shemot 7:19), as well as by Rav Avigdor Miller, who offered the following description of the plague:

It was not blood that could be used for transfusions or for fertilizing the land, but the resemblance was close enough to sicken the spectators. A revolting miasma came up from all the streams of Egypt, and the people lost their appetite, and vomited again and again at the sight and odor of the revolting liquid. Normal life in Egypt came to a shocked standstill; and thirst, now the first time in their history, became the chief matter in the land. Everywhere, the infirm and aged lay dead; and the nation groaned in the depths of despair.[3]

If the water did not change to actual blood, then through which natural processes did Gd cause the waters to appear blood-like?

Rav Munk [1] mentions the possibility of aquatic vegetation causing the Nile River to turn a pale red in color. Secular scientists have offered a variety of possibilities, including the deposition of red meteorite dust from a passing comet, deposition of volcanic ash, the intrusion of red silt, and the contamination of the Nile River by red-pigmented flagellated protozoa, zooplankton, dinoflagellates, microfungi, and cyanobacteria [5,6].

This last hypothesis, a sudden overgrowth of an aquatic microbial species, may have the most merit. Although it receives little publicity because of the potential negative impact on tourism, the Florida coastline often experiences red tides caused by a bloom (population explosion) of Karenia brevis, a red-colored dinoflagellate. This alga produces a large number of neurotoxins, some of which become airborne, and when a red tide coincides with an onshore breeze, hospitals in Florida prepare for an influx of patients. Brevetoxins constrict pulmonary (lung) bronchioles and are thus extremely harmful to asthmatics and others with breathing problems [7]. Other red-pigmented dinoflagellates, including species of Gymnodinium and Gonyaulax, are also involved in these blooms and produce various neurotoxins which are harmful to fish and other aquatic vertebrates [8].

Apparently, the Nile River could not maintain such massive numbers of dinoflagellates, and so they died. The death of a massive amount of algae, and their subsequent decomposition by aquatic bacteria, would lead to the generation of malodorous air pollution. As noted, each of the ten plagues had several subcomponents that added to the misery of the Egyptians, and emissions of aquatic and airborne toxins generated by red-pigmented dinoflagellates would be a deleterious subcomponent of the plague of blood.

The issue of whether the water of the Nile River turned to actual blood or to a substance resembling blood, may affect our understanding of the Torah’s account of the fish’s death. Rav Sorotzkin [4] notes that if the Nile River turned to actual blood, the befouling of the Nile River may have resulted from the blood’s bacterial decomposition. The fish were unable to live in blood and in an aquatic ecosystem made anaerobic by excessive bacterial metabolic activities, and thus perished. The bacterial decomposition of the fish added to the malodorous emissions from the Nile River, thus exacerbating the already intolerable stench.

Regardless of whether the Nile River was transformed into actual blood or into a blood look-alike, the plague sent a powerful message to the Egyptian population, who worshipped the river as a god. They would prostrate themselves to the river first thing in the morning, viewing it as the god who provided them with a livelihood [4]. This so-called god was now transformed into a stinking cesspool!

Did the Egyptians Drink Blood?

As cited above, the Torah relates that the Egyptians “could not drink from the waters of the river” (Shemot 7:24). At first glance, this means that the Egyptians could not drink from the Nile because its water had turned to blood, which is not drinkable.

As several commentators noted, however, this is incorrect. Blood can, in fact, be ingested by human beings. Human hematophagy is the practice found in certain societies to drink blood and to use animal blood in food items. The African Masai, for example, drink a liquid composed of a mixture of cow milk and cow blood, and many communities throughout the world consume blood sausage. Ritual hematophagy is also observed in some societies. The Scythians, a nomadic Russian people, drank the blood of the first enemy killed in battle [9].

Therefore, the commentators offer different interpretations of the Torah’s description of the Egyptians’ inability to drink the waters of the Nile during the plague. Rav Munk [1] explains that the Egyptians could not endure seven days drinking only blood, without water, and they therefore had to seek alternative sources for water. Rav Chaim Rabinowitz, in his Da’at Sofrim commentary, suggested that the thirsty Egyptians, hoping that the waters only appeared red but were not actually blood, drank from the Nile River. The water was, in fact, blood, and the ingestion of blood intensified their thirst. Thus, although they were able to drink the Nile’s waters, they were unable to quench their thirst with this water.

Rav Dovid Cohen (Simhat Yavetz commentary to the Haggadah) explained, based on a careful reading of the Torah’s account, that the Egyptians were unable to drink from the Nile because of the pollution caused by the decaying fish, and not because the water had changed to blood. This observation is also made by Rav Yaakov Tzevi Mecklenburg [10], who writes:

In the worst emergency, the people could have drunk blood. If blood were not considered a drink by the Torah, its consumption would not have been forbidden on pain of death. This is why the Torah mentioned not only the fact that the water would turn to blood, but that the fish of the river would all die. Once the river would be full of blood plus rotting carcasses of dead fish, even the option of drinking the blood would not exist.

Second plague: Frogs

“Hashem said to Moshe: Say to Aharon: Stretch out your hand with your staff over the rivers, over the canals, and over the reservoirs, and bring the frogs over the land of Egypt.” (Shemot 8:1).

How Did the Frogs Survive the Plague of Blood?

The frogs that descended upon Egypt originated from the Nile River, clearly indicating that they had survived the plague of blood. Although the fish died as a result of the water’s transformation, the frogs lived.

Fish absorb dissolved oxygen through their gills, and thus their death may have stemmed from the lack of suitable quantities of dissolved oxygen in the Nile River. Bacterial decomposition of the dead fish would have further depleted the waters of their dissolved oxygen, thus causing even more fish to die. Frogs, however, are amphibians and are not confined to an aquatic system. Hence, if the surrounding vegetation remained moist, they could have survived as terrestrial denizens during the week of the plague. Alternatively, as frogs have lungs, they could have remained in the anaerobic water of the Nile River and come to the water surface to breathe air. Frogs also have two other modes of gaseous respiration (in addition to pulmonary respiration). Their moist skin is supplied with capillary blood vessels, allowing for cutaneous gas exchange when in water or on land, and gas exchange also occurs across the moist surfaces of their mouth and pharynx [11].

What Were the Tzefardea?

Gd tells Moshe to warn Pharaoh that if he refuses to release the Hebrew slaves, Gd would “strike all of your territory with frogs” (Shemot 7:27). Rav Miller [3] understood the phrase “all of your territory” to mean that Egypt was overrun by  not only aquatic frogs, but also various species of terrestrial frogs and land toads. In particular, Rav Miller makes note of the Bufo marinus, a giant toad which consumes birds and small mammals, and has poisonous cutaneous glands that secrete a deadly toxin when it is stepped on. Another usually large amphibian is the Goliath frog, Conraua goliath, which is more than 12 inchs long and can weigh up to eight pounds. This giant frog devours animals such as rats and ducks [12], and may also have been involved in the plague.

It is interesting to note that some commentaries, including Rabbenu Bahya, the Ramban (see Munk [1]), and Seforno (Shemot 8:3), interpret the term tzefardea – the word used in reference to the second plague – to mean crocodile. The Netziv (Ha’amek Davar, Shemot 7:28) suggested that this plague included both frogs and crocodiles, with frogs infesting the entire country of Egypt, and crocodiles invading Pharaoh’s palace.

Frog Cloning

In describing the onset of the plague, the Torah writes, “Vata’al hatzefardea – The frog ascended [from the river]” (Shemot 8:2), implying that the plague began with but a single frog. Rashi cites the Midrash as explaining that indeed, just one frog initially emerged from the Nile River. The Egyptians struck the frog, attempting to kill it, whereupon it fragmented into many frogs. The Midrash’s account, at least on the surface, appears to describe cloning, the process through which differentiated adult cells become embryonic or totipotent to develop into copies of the original organism.

Interestingly, decades before the widely-publicized cloning of the lamb Dolly, the first successful cloning experiments, developed in the 1950s by Robert Briggs and Thomas King, were with frogs (Rana pipens) [13]. With this in mind, and probably pushing a scientific explanation to its extreme, striking the initial frog may have caused shedding  of its differentiated epidermal somatic cells, which became totipotent or zygote-like cells, undergoing mitotic divisions to generate multicellular frogs.

Physical and Psychological Torment

Besides causing the Egyptians physical discomfort, the frogs and toads were also used as a powerful weapon of psychological warfare. Male frogs and toads croak and call vociferously to attract females (Hickman et al., 2005). Upon hearing the loud, incessant croaking, the Egyptians believed that the frogs were the reincarnation of the Hebrew babies that had been cast into in the Nile River, who came back crying out for their blood to be avenged [3].

Pharaoh eventually implored Moshe to eliminate the plague of frogs, and Moshe prayed to Gd. In response to Moshe’s prayer, Hashem caused all the frogs to die, after which the Egyptians “piled them up into heaps and heaps, and the land stank” (Shemot 8:10). Thus, the pollution of the atmosphere initiated through the rotting fish in the Nile River from the first plague now continued throughout the entire country, as the frogs slowly decomposed in the hot Egyptian climate.


In the first two plagues, Hashem launched a debilitating attack on Egypt using components of nature as the invading army. In addition to inflicting grave physical, psychological and economic damage, these plagues also dealt a severe blow to the various components of the Egyptian biosphere: the aquatic ecosystems – the waters of the Nile River changed to blood or to a blood-like substance; and the atmosphere – the air became polluted with malodors emanating from rotting fish and frogs.


1.Munk, E. , The Call of the Torah, Volume 2, Mesorah Publications,Ltd (Brooklyn, 1993).

2. Dessler, E.E., Strive for Truth, Volume 2. Feldheim Publishing Company (New York, 1999).

3. Miller, A., Narrate to Your Son, Yeshiva Gedolah Bais Yisroel (Brooklyn, 1992).

4. Sorotzkin, Z., Insights in the Torah, Volume 2, Mesorah Publications,Ltd (Brooklyn, 1993).

5. Marr, J.S. and C.D. Malloy, “An Epidemiologic Analysis of the Ten Plagues of Egypt,” Caduceus 12:7-24 (1996).

6. Trevisanato, S.I. (2006). Treatments for burns in the London Medical Papyrus show the first seven biblical plagues are coherent with Santorini’s volcanic fallout. Med. Hypothes. 66:193-196.

7. Potera, C., “Florida red tide brews up drug lead for cystic fibrosis,” Science 316:1561-1562 (2007).

8. Willey, J.M., Sherwood, L.M., and C.J. Woolvertoon, Prescott, Harley, and Klein’s Microbiology, McGraw Hill (New York, 2008).

9. Wikipedia (retrieved in 2006),. http://en.wikipedia.org/wiki/hematophagy.

10. Munk, E.., Haketav Vehakabbalah. Torah Commentary by Rabbi Yaakov Tzevi Mecklenburg, Lamda Publishers (New York, 2001).

11.  Miller, S.A. and J.P. Harley, Zoology, McGraw Hill (New York, 2005).

12. Hickman, C.P., Roberts, L.S., and A. Larson, Animal Diversity,  McGraw Hill (New York, 2003).

13. Gilbert, S.F., Developmental Biology, Sinauer Associates, Inc. Publishers (Sunderland, 1994).

This article was adapted from an analysis written by Rabbi Harvey Babich, Ph.D which appeared in Volume 12 of Derech Hateva.