---
title: Siman 463–466 – Flour, Saliva, and Related Laws
description: "הChelek 5 1. If you ever find a pocket of flour in a baked matza — do not put it into gravy. If you do, it will turn chometz and the food will become ossur b'hano'ah. (Siman463 — MB )…"
url: "https://mishnaberurasummaries.com/docs/siman-463-466-flour-saliva-and-related-laws/"
updated: "2026-07-27"
category: Laws of Pesach – Matza
---

# Siman 463–466 – Flour, Saliva, and Related Laws

הChelek 5

1. If you ever find a pocket of flour in a baked matza — do not put it into gravy. If you do, it will turn chometz and the food will become ossur b'hano'ah. (Siman463 — MB )

1. Saliva from humans and farm animals can cause grain flour to leaven. Steam can cause grain flour to leaven. (Siman466 — ShA ,  — MB )

1. The poskim argue about dampness that 'sweats' from walls. Lechatchila, do not use flour that became wet with such moisture. (ShA  — MB )

1. Using a gentile's chometz medicines to heal illness or wounds is allowed if there is no alternative way. You do not own the chometz and the issur hana'a is only mid'rabbonon. (MB )

1. If there is danger to life you are allowed to benefit from chometz and even eat it if there is a chance it will help. If there is no danger to life even a crumb is ossur. (MB  — ShaH6)

1. The following fluids can leaven just like water: (1) dew; (2) urine; (3) fluids from the nose, mouth, eyes, and ears; (4) runny bowels. (ShA  — MB , )

1. The following fluids do NOT cause chometz: blood, milk, fat, bile, sweat, excrement. (ShA  — MB , , )

## Key

**ShA**
 : Shulchan Aruch

**MB**
 : Mishna Berura

**ShaH**
 : Shaar Hatsiun

**ShaT**
 : Shaaray Teshuva

**BeH**
 : Beur Halacha

**BaH**
 : Baer Haytayv

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